How Sir Nigel Gresley Class A4 steam locomotives were built for speed

Up to that time, many of the company’s major expresses had been quite pedestrian. Thus, Gresley was tasked to design a new locomotive.

He produced the A4 Pacific (a 4-6-2-wheel arrangement) and no. 2509 Silver Link was the first locomotive of this class to leave Doncaster Works in early September 1935.

Its appearance was rather unusual since the smokebox, boiler, running boards, cylinders and chimney were enveloped in a streamlined casing.

The design of the front end of the A4 was inspired by the Bugatti petrol railcar used on the Paris-Deauville route by the État (State) Railway. Gresley had personally travelled in the railcar with his assistant O.V.S. Bulleid and Ettore Bugatti himself.

The latter had been originally involved in the construction of luxury motor vehicles and racing cars before being forced to diversify with the railcar.

Inevitably, he took the lead from the road and used four car engines, amounting to some 800 horsepower, to provide traction for the railcar and a top speed of 100 mph was possible.

Bugatti had previously reached a speed of 107 mph on the road with the Type 32 race car of 1923 and this had also utilised a wedge-shaped design at the front end.

Another new form of transport to influence Gresley was the aeroplane, particularly the aerofoil (or wing), which was incorporated into the design of the A4’s running plate and side skirts.

A silver grey paint was chosen for the engine, tender and wheel centres, black for the front of the wedge and battleship grey for the side skirting.

The new high-speed service between King’s Cross and Newcastle was called the ‘Silver Jubilee’ to honour the 25 years that King George V had spent on the throne.

A ‘Silver Jubilee’ coach set was ordered from Doncaster Works in February 1935 and comprised seven vehicles, with two articulated pairs and a triplet set.

These were in turn split, respectively, to a third-class brake, third-class corridor and first-class semi-open, first-class brake, with the third-class restaurant, kitchen car and first-class restaurant contained in the triplet unit.

The press demonstration run of the new ‘Silver Jubilee’ express train hauled by no. 2509 Silver Link occurred on September 27, 1935.

Departing from King’s Cross station’s platform 6 at 14.25 for Grantham, the locomotive delivered an unprecedented performance in reaching 112½ mph twice – a new world record – and maintaining high speed over a large portion of the journey.

Driver Taylor and fireman Luty managed to deliver the train to Grantham in 88 minutes 15 seconds for the 105 miles, which was around the schedule, although signals and speed restrictions stopped faster running.

Driver Taylor, who later received an MBE for his exploits, was heartily congratulated by Gresley.

With the ‘Silver Jubilee’ train, there was widespread public interest as people lined the route – waiting both at stations and trackside to see the ‘A4’ storm past – and the event received heavy publicity, which was increasingly becoming a tool to be exploited.

The ‘Silver Jubilee’ train and Silver Link proved a success, as did the three other A4s introduced by the end of the year, and the LNER was confident that similar trains – and locomotives – would prove lucrative for the company.

By the end of 1938, two new services were running – the ‘Coronation’ and ‘West Riding Limited’ – and 35 A4s were in traffic.

An enthusiast and historian of the LNER, K. Risdon Prentice, realised that no. 4498 would be the 100th Gresley Pacific when completed at Doncaster in late 1937.

He suggested to the authorities that this should carry the name of the locomotives’ famous designer which was enthusiastically accepted. An official naming ceremony was carried out at Marylebone station on 27th November 1937.

Towards the end of the A4 construction programme, Gresley tested the Kylchap double blastpipe and chimney with the A4 design and four locomotives were fitted.

The first was no. 4468 Mallard. During 1938 there was a feeling that an LNER locomotive could go faster than the current British record.

A high-speed test was arranged – in much secrecy – for Sunday July 3, 1938. To make sure that there would be no doubt as to any records set up, the dynamometer car was sent south from Darlington to be used with the test.

The locomotive specially chosen for the task was no. 4468 Mallard. Driver Joe Duddington and fireman Tommy Bray had been allocated Mallard at Doncaster from new and were quite familiar with the individualities of the engine.

Driver Duddington was also known to be a man who would push an engine to the limit if necessary.

On that Sunday, Mallard and the train left a siding at Wood Green station and headed north to Barkston.

At 4.15pm, Duddington turned his cap back to front and opened the regulator full to begin the record-breaking speed attempt.

In time, a peak of 125 was maintained for 306 yards close to milepost 90. The boiler had been steaming at about three times the normal rate at this point and the wheels were turning at 8½ revolutions per second.

Then the train pulled in at Peterborough, assistant CME D.R. Edge telephoned Gresley with the record-breaking news and, while his reaction has gone unrecorded, it can be imagined how pleased he must have been.

At King’s Cross, the press was out in force and even though the train had returned Mallard was not present (the official statement was that it had duties to perform elsewhere).

Journalists were ushered into the dynamometer car to see the evidence that a speed of 125 mph had been reached.

This figure was the one given by the LNER and Gresley and not 126 mph, as later declared by British Railways on the commemorative plaques fitted to the Mallard boiler.

The figure of 126 mph was a possible maximum for one second, but Gresley would not claim this because the time period was too short.

A total of 35 ‘A4’ class Pacifics were in traffic for the summer of 1938 and these were working the LNER’s principal expresses.

On August 31, 1939, the last streamlined trains operated before the War. A total of 1,952 ‘Silver Jubilee’ trains ran between 1935 and 1939, and according to Locomotives of the LNER Part 2A the most active was no. 2509 Silver Link with 564 journeys completed (with a further 44 appearances on the other streamlined services)

A4 no. 4469 Sir Ralph Wedgwood had only been in traffic for 12 days after a General Repair in April 1942 and was being held at York shed overnight while being run in.

On April 29, York was targeted in a bombing attack. Many places were hit, including the railway station and the locomotive depot, where no. 4469 was resting. The right-hand side of the engine took the force of a high-explosive bomb, causing irreparable damage.

Several A4s met their fate at the end of 1962 and withdrawals progressed through to 1966.

A small band of locomotives established an enclave in Scotland during this period and managed to survive on the Glasgow to Aberdeen expresses, continuing the standards established on the East Coast Main Line.

Thankfully, six A4 locomotives were saved from the scrapyard to represent the class for posterity. Several have been active on the main line in recent years, allowing new generations of enthusiasts to experience the thrill of an A4 in steam and at speed.

Further reading: John Ryan Gresley’s A4s (2020)