Trackside Classic: 1976 British Rail Inter City 125 High Speed Train – Still Setting The Standard


(first posted 10/18/2015)    In 1995, British Rail didn’t celebrate the twentieth anniversary of their pride and joy, the Inter City 125 diesel train, as ‘we don’t want passengers to realise how old it is’. Well, twenty years further on, the Inter City 125 (or HST, for High Speed Train) is still the best way to travel Britain’s rails, it still has another 20 years left, and passengers still don’t realise how old it is. So let’s celebrate this, the fastest diesel train in the world, and review its life story.


In the 20 years after the war, the domestic travel market in the UK, as elsewhere, was transformed. Motorways spread their tentacles and bypasses cleared bottlenecks; by 1970, car ownership had increased by five times since 1945. Although British Railways (BR) had eliminated steam, train speeds lagged, with only the 100mph electric expresses from London to Birmingham and Manchester and the mighty Deltics being a credible competitor in the speed stakes; other routes reached only 90mph. A step change was needed if long distance train travel was to survive into the 1970s – but without the funds or political will to build new express lines like France and Japan, the new trains had to deliver accelerated performance on existing infrastructure, and around existing slower passenger and freight traffic.


The first answer proposed to this conundrum was the gas turbine powered Advanced Passenger Train (APT-E, for experimental), which was commissioned from the BR research engineers, with a brief to think outside the railway box. The APT thus drew from aerospace technology, majoring on aluminium for lightness. Disregarding the gas turbine, which was not intended for series production, the great innovation was the ability to tilt, to allow the train to take corners more quickly than a conventional train without the need to realign curves. Using tilt and hydrokinetic brakes, the APT-E could reach up to 150mph on existing lines but still stop in the same distance as conventional trains. It clearly showed that the ideas behind it had potential once it emerged in 1972, after several years in development, but was far from a practical or affordable option for mass production.


Tilting had a weakness, beyond the alleged travel sickness. The cramped confines of Britain’s railway structures – a downside of being the pioneer – meant that the profile of the APT narrowed above the waist, restricting interior room. But that was the least of its problems, as perhaps predictably, it was too advanced and expensive for the real world. Traditional railway engineers in BR had been sceptical from the start, and in 1969 had successfully lobbied the board of British Rail (as it became in 1964) to start parallel development of a more conventional diesel powered alternative shortly after the APT project commenced, to hold the fort until the real APT was ready.


This emerged in 1972 in prototype form as the High Speed Train (HST) – just 22 months after approval of the project. Compared to the APT, this was a decidedly conventional train – but a very thoroughly engineered one, from a team led by Terry Miller, Chief Engineer (Traction & Rolling Stock) of BR.


To produce the high power needed to propel an eight or nine coach train at 125mph, Miller needed 4,500hp, compared to the Deltic’s 3,300. No suitable power unit existed, so,  two power cars were used, one at each end and linked by electronic control systems.


BR had used this idea before, with mixed results, in the ‘Blue Pullman’ of 1960. The concept has numerous advantages – it reduces the weight of the power car to something that virtually every line in Britain can accept without expensive strengthening of the track and bridges (an HST power car is just 70 tons – barely half the weight of existing 2,200hp diesels); it maximises flexibility – no need to run the engine round the coaches, just drive from the other end; and reliability, by having in effect two separate locomotives – and one was enough to propel the HST at 100mph; unlike conventional diesel multiple units, there are no engines under the floor of the coaches, so no noise or vibration for passengers; and it allowed for the train to styled in a cohesive and dramatic way, with power cars and coaches sharing the same profile and livery.


The chosen engine was the Valenta, produced by the Paxman engineering and diesel engine company. Then a subsidiary of English Electric, and later one of the constituents of the Alstom Group, the business is now part of the MAN group. The Valenta is a V12 four stroke turbo-charged and intercooled diesel, with a capacity of 79 litres (4,800 cu in). As installed in the HST, the engine in each power car produced 2,250 hp (1,680kw). Power is passed to the four tractionn motors on each power car through a Brush Traction generator.

And it has one of the most penetrating exhaust notes ever heard – maybe not as pleasing to an engineer as a Deltic’s gearing based roar, but impressive nevertheless to platform observers – the famous ‘Screaming Valenta’. Target speed was down from the APT, of course, to 125 mph, but the higher speed and superb acceleration still allowed huge cuts in journey times.


Between the two power cars were BR’s new Mark 3 coaches; these were a brand new design, designed for 125 mph running and solidly constructed in a steel monocoque engineered for strength and crashworthiness, and, at 23m (75ft) long, 3m longer than previous coaches. The Mark 3 was the first British coach to feature such things as double glazing, full air-conditioning and air based suspension. Crucially, they were fitted with disc brakes, not the clasp brakes of older stock, which enabled the HST to be brought to a halt from 125mph in the same distance as a Deltic from 100mph. This meant no need to replace the lineside signalling. The Mark 3 is also, compared to the APT, spacious, with no narrowing profile as the HST was not designed to tilt. The meticulously developed and tested suspension and bogie (American – truck) design gives a very smooth ride on even indifferent track, and the spacious seats are an indictment of virtually every train built since. Even 40 years on, they are a superb vehicle, and stand comparison with anything in the world outside the Japanese Shinkansen, French TGV and German ICE fleets.


All the seating was in open coaches – 2+2 for Standard and 2+1 for First – around tables and with all seats aligned to fit the window spacing (you’d be amazed at how hard it can be on a modern British train to get a seat with a window rather than pillar view!).


This meant the final demise of the traditional railway compartment, seating 4 or 6 passengers depending on class in an enclosed compartment accessed from a corridor along one side of the coach – a layout that dated back to the earliest days of the train, but clearly didn’t suit modern needs.


Truth be told, the looks of the prototype power unit were not its best feature. The cab was designed to accommodate a single centrally seated driver – something the trade unions promptly refused to accept, insisting on the traditional two man crew – and the side windows were deliberately set behind the driver’s field of vision to avoid the distracting phenomenon of ‘sleeper flicker’ – the constant flashing of sleepers (American – ties) in the corner of the driver’s eye. This, plus crash protection, meant a heavy looking frame around the central window, exacerbated by the mandatory bright yellow paint. The livery of standard BR passenger blue and grey, but with the two colours reversed, didn’t help; the power car lacked presence and gave little impression of speed or power.


But the performance was stunning. Pretty much straight out of the box, it demonstrated that a sustained 125mph was possible on existing track, safely, smoothly and comfortably, and with impressive acceleration and braking. The prototype was extensively tested on the Western Region of BR, between London Paddington, Bristol and South Wales, which would be the first route to receive the new trains, and, in June 1973, it achieved a world diesel train speed record of 143.2 mph on the Eastern Region racetrack north of York.


Series production of HST power cars began in 1974 at the BR works in Crewe, where the Grand Junction Railway began building steam locomotives in 1840. The Mark 3 coaches, built at the former Midland Railway works in Derby, were little changed from the prototype, but the power car was dramatically restyled by Kenneth Grange, one of Britain’s leading industrial designers.


Considering he was better known for such classics as the Kenwood food mixer, the angle poise light and the standard British parking meter, picking him for the HST was a gamble – but one that paid off brilliantly.


The production HST looks fast and modern, even now. The sharply angled nosecone (a one piece GRP moulding) was aerodynamically better than the prototype’s blunter prow, and Grange accentuated the impact of the shape by using bold yellow around the nose and down the flanks, ending at the Rail Blue radiators, which hinted at the power lurking within and blended neatly into the blue and grey coaches. Conventional railway couplings were replaced by an emergency coupling hidden behind the smoothed front panel. And just in case you were in any doubt, the new name Inter-City 125 was prominent on the side of the power car and on each coach. Passengers could see they were being invited aboard something new and special – but without paying a premium fare – the HST has always been a standard fare train.


Fleet operation of the Inter City 125 began on BR Western Region in October 1975, and by May 1976 27 sets were in service. Each set had 8 Mark 3 coaches, including First and Second (soon renamed Standard) class seating and a restaurant / kitchen or buffet car.


Journey times from London to Bath, Bristol, Cardiff and Swansea were slashed by a quarter and passenger numbers soared – known as the ‘nosecone effect’.


From 1977, HSTs were introduced on the East Coast route north from King’s Cross to Yorkshire, Newcastle upon Tyne and Scotland.


The big acceleration on that route came in 1978, when almost an hour was cut from London – Edinburgh times and the service frequency increased. By 1982, HSTs had appeared on the Midland mainline from St Pancras to the Midlands and Sheffield, and the Western Region had enough sets to replace 100mph loco-hauled trains west of Bristol to Exeter, Plymouth and Penzance.


It wasn’t just passengers that loved them, either; drivers queued for the normally less popular long distance assignments once HSTs were assigned to a route, and on-board crews appreciated the much better working conditions compared to the stock they replaced.

Ultimately, 95 sets of Mark 3 coaches and 197 power cars were built, and both the East Coast and Western mainlines strengthened trains to 9 coaches. All of Britain’s express routes saw them in regular service right through the 1980s and 1990s, except the electrified West Coast from London Euston to north west England and Glasgow, and even on journeys such as Aberdeen to Penzance, where the scope to exploit their speed was limited in many places, the enhanced environment won back passengers.


HSTs have always been intensively worked – most run 1,000 miles every day, and on the East Coast, one diagram runs from Leeds in Yorkshire to London, to Aberdeen in north east Scotland, back to London and then back to Leeds – something over 1,500 miles of high speed work in 18 hours!


Outside the south east of England’s third rail commuter network, HSTs have been regularly used on virtually all the main lines in Britain over the years. Today, the HST is still (for a few more years) the mainstay of the routes to the west from London Paddington, and north from St Pancras. The Cross Country network, centred on Birmingham, is also a key user and they remain as the second string on the East Coast. Together, these operators take the HST every day to Inverness in the Scottish Highlands; Penzance in Cornwall; Fishguard in south west Wales; and Hull on the Yorkshire coast, and virtually everywhere in between. Not bad for something designed as a stopgap 40 years ago!


Inevitably, there have been reliability issues over the years, most notably with overheating in the exceptional summer of 1983, but these were largely resolved by tightening inspection and maintenance procedures. Other issues have been caused by the hard life the engines get – constantly cycling from full power to coasting and back, as frequently as every 5 minutes on some routes.

And by the early 1990s, it was apparent that while the train had a long life left in it, the Valenta was past its peak – too noisy, dirty and fuel-hungry for the 21st century, and increasingly hard to maintain. So re-engining became the game, with the first trial of a new Paxman engine, the VP185, in 1994 leading to a programme to re-engine the Midland Mainline fleet of 24 power cars. Operators elsewhere preferred the MTU V16 4000 engines, and there are now 170 power cars using that engine. The last Valenta was replaced in 2010.


The HST does have two basic problems, which both date it and show that, ultimately, it was built to a budget. To open the doors from the inside, you had to open the window and lean out and grasp the external handle – just like in George Stephenson’s day. To be fair, an interior handle and locking mechanism was fitted in the 1990s – not for convenience, but for safety, to ensure doors shut fully and couldn’t open at speed. And the toilet discharges direct onto the tracks beneath. Yes, in the 125 mph masterpiece, you still cannot flush when the train is stationary. Both these need to be fixed if the trains are to fulfil their potential to last another 20 years – and can be. After all, Hitachi turned one into a diesel-electric demonstration prototype.


Since privatisation in the 1990s, HSTs have appeared in the liveries of at least twelve private operators at various times, some better than others – a bewildering kaleidoscope to the ordinary observer. This, and a variery of interior refits, may have helped it stay fresh in the eyes of the travelling travelling public, and let them mistake its age – unlike in BR days, the HSTs on each route look different inside and out.


Many will remember fondly the smart and well maintained dark blue and red of Great North Eastern Railway, but my favourite is the BR Inter City division’s dark grey and white with red detailing applied from the mid-1980s onwards – a traditional two tone railway style that emphasised the smooth lines and length of the train and stood out from the plainer blue and grey of the lesser trains around it.


There is even an all-over yellow one today, used by the infrastructure owner Network Rail as a track measurement train; it covers all the mainlines of Britain every 13 weeks, checking and recording track geometry at high speed.


Through the 1980s and 1990s, BR exploited the HST ruthlessly in its marketing, producing some great posters and TV spots. It also made sure that periodically a new high speed record would be set, usually to promote new services. In September 1985, the new Tyne-Tees Pullman covered the 268 miles from Newcastle to London in 140 minutes at an average speed of 115.4 mph. An 18 mile stretch near Peterborough was covered at an average of 140.1 mph. And in November 1987, power cars 43102 City of Wakefield and 43104 with three coaches set a new world speed record for diesel traction of 148 mph between York and Northallerton – a record that has yet to be verifiably broken.


We have all had our favourite HST journeys over the years, from marvelling at the novelty of smooth, quiet high speed travel in the early days, to the time an American visitor insisted on standing in the aisle of a GNER express as ‘the trains going past the other way are way too close and way too fast’. Explaining the closing speed of 250mph amused her partner, but she didn’t sit down until we were an hour out of London.


But my favourite memory is an evening journey from London to Edinburgh, in the mid-2000s. Diligent online hunting for advance fares made first class train travel cheaper and faster than flying down to the capital on business; southbound was the 0600 Flying Scotsman from Edinburgh, formed of one of the new Class 91 electric sets – no faster than a 125, but bouncy and cramped. Coming back, a GNER express to Aberdeen – guaranteeing an HST as the electric wires stop at Edinburgh – leaving around 1630. No commuters, as first stop is York, 200 miles north.


And the last coach was almost empty – a table for two at the very rear of the train to yourself.

Leave the door window open as you board, and you get the full Valenta roar as the train accelerates up the steep incline through the tunnels out of King’s Cross, then sit back and relax. Spread out, recline the seat, perhaps; enjoy the at seat drinks service from the attentive stewards. Then, after York, move forward to the Dining Car for the best train food in Britain- a leisurely three course dinner, with not a drop of wine spilt, as we skim across the Vale of York at two miles a minute (or more, if time needs to be made up).


A low sun emphasises the dramatic sight of Durham Cathedral (‘half church, half castle against the Scots’, say the guidebooks) and the always stunning sight of the six great bridges across the River Tyne as we snake in and out of Newcastle Central. North of Newcastle, there are some great coastal views and then along the cliffs north of Berwick upon Tweed as the speed drops and the line curves through the hills of the Scottish Borders, before  we finally emerge into the dramatically located Edinburgh Waverley, four and a half hours from London. Beats an hour on the Underground to Heathrow, two hours queuing and an hour and a half squashed in a 737 every time.

Britain’s pre-eminent authority on modern railway engineering, Roger Ford of Modern Railways magazine, has said ‘the HST remains the standard by which all other trains are judged’. How right he was – and nothing has matched that standard yet.