Kayden's Wheel Reports: Thompson's A1/1

Railway enthusiasts are some of the most passionate people on the planet, and we're not afraid to make our opinions known. While we may come from different places and walks of life, opinions about the more well known figures and locomotives have become extremely widespread, and with the advent of social media and the Internet, the spread of these opinions has only increased.

One of these is concerning Edward Thompson (1881-1954), the Chief Mechanical Engineer of the London and North Eastern Railway from 1941 to 1946, who's tenure has been the subject of much controversy, primarily concerning his rebuilds of various designs from his predecessor, Herbert Nigel Gresley (1876-1941).

Many railway journalists, historians and even ex-railway staff have thus criticised Thompson as 'attempting to rid the LNER of Gresley', doing what he did merely to befit his twisted goals of ridding the railway of his predecessor's influence. Resultantly, most enthusiasts share the view that his rebuilt designs were 'ungamely' and 'ugly'. 

But upon further research, his work does hold at least some merits, especially concerning the subject of this post, that being his A1/1. 

In 1945, Thompson instructed G. A. Musgrave, the shed manager of Kings Cross Shed (known as Top Shed by enthusiasts) to select a Gresley A1 locomotive to be rebuilt to test features that were to be implemented into a brand new class of top-link express locomotives that Thompson had in mind. Musgrave merely selected 4470 'Great Northern' as she was the oldest (being built in 1922), and naturally the most worn out member of the class. 

Rebuild, however, is a somewhat loose term, as Thompson only used the minimum number of components from the original locomotive to class it as a rebuild, but many have described it as the 'Post War A4', using a derived boiler, Kylchap double chimney and frames of A4 design. This disproves the argument that Thompson wanted to rid the LNER of Gresley, for he had marked the A4s as a standard class to be developed further. 

Both locomotives used 3 sets of cylinders and valve gear, two outside the frames and one inside the frames. Where the A1/1 differed from the A4s however, was in the displacement of Gresley Conjugated Valve Gear. This involves a bar lodged across all three sets of valves and utilises the motion of the two external ones to drive the middle one. This was developed by Nigel Gresley with assistance from Harold Holcroft, then working for the South Eastern and Chatham Railway. It was a reliable system, provided it was being maintained, at which during the Second World War with a reduced workforce and standard of maintenance, this was simply not an option. An assessment by William Stanier from the London Midland Scottish (the LNER's biggest rival for passenger traffic to Scotland) recommended its use to be discontinued due to the sheer number of failures recorded, its findings so embarrassing that the LNER mandated said report was NOT to be released to the public. 

This explains the A1/1's cylinder placements, which like all of Thompson's Pacifics, used 3 sets of Walschaerts instead. However, one area of criticism I can accept was his use of conrods (the connecting rod in the motion that drives the wheels directly) of equal length, which required moving the middle cylinder further forward and the external ones further back, thus, with its extended smokebox, creating an 'elongated look' and give the locomotives poor weight distribution and adhesion, thus the numerous accounts of 'wheelslip'. 

However, this cylinder placement was quite common on the Great Western and London Midland Scottish, as well as Continental Europe, especially in France. Stanier himself was also frequently consulted for the project and advised Thompson on a lot of aspects of the design too. Of course, beauty is in the eyes of the beholder, but I cannot possibly fathom how it is acceptable on some locomotives, but not on others.

So how did she (engine drivers often address their locomotives as female) measure up to her peers? Well, after some initial teething troubles (primarily a drafting problem with the double chimney that were resolved with the addition of smoke deflectors), she was more than capable of matching the later A4s, able to keep to their schedules when asked to fill in for them or even arriving earlier than expected. She also quite literally went from being the worst performing Pacific locomotive on the LNER, to being the best until the Peppercorn A1s came about. 

Unfortunately, the LNER's policies mandated that Thompson had to retire in 1946 at the age of 65. His successor, Arthur Peppercorn only had 2 years as CME and with a limited budget and resources that Post War Britain could allot to him, he was forced to cut back on the project, instead opting to increase the drive wheel diameter on his A2 design (also of Thompson influence) to create the aforementioned A1s.

The A1/1 would be renumbered into 60113 upon nationalisation of all the major British railway companies into British Railways, where she would work in relative silence with her Gresley and Thompson cousins and colleagues on the East Coast Main Line until her withdrawal in 1962. There was a failed preservation attempt following her retirement, albeit with plans to rebuild her back into her Gresley form.

Final Thoughts

I find the story of the Thompson A1/1 fascinating and believe her story is one that is largely misrepresented by popular lore. Many think as a one off, she had no room for error, but in reality, she as intended as a test bed for something larger that Edward Thompson had in mind and what he had to deal with, she is a true testament to his engineering knowledge and intellect, and dare I say it, a symbol of British engineering excellence during a time of war. 

Before I sign off though, I do NOT claim to be an expert on railways or engineering, I merely read and repeat things I have learnt in ways that I hope are presentable to at least a good majority of people. This locomotive is a personal favourite of mine and it pains me to see her misrepresented in media. I hope this article and all works written about her by other writers such as Simon A. C. Martin and Tim Hillier-Graves will go at least some way in correcting this and ensuring the unwarranted hate Thompson has received will be disproven.

(An unknown artist's colourisation of the A1/1 in her later condition with smoke deflectors, wearing her as-built livery with Great Eastern Railway Prussian Blue, intended to commemorate 3 of the companies that would form the London and North Eastern Railway, Original B&W Picture taken by the LNER in 1946)