Having read through all three topics and IMO to understand the factors faced by Robert Riddles in his new job between 1948 and his early retirement in 1953, we need to look at the bigger picture.
Almost all the factors listed below are somewhere here on RMweb, but not altogether as below.
I'll also post some biographical detail of Robert Arthur Riddles in this topic. IMO, information relevant to his attitude to the tasks in hand is missing from all the discussions.
1. During the period of Riddles tenure of office (1948 - 1952) Britain was broke and borrowing from the U.S.A. to aid recovery from the 1939 - 1945 World War. Many commodities were in short supply and some items continued to be rationed throughout the period. The Government had restrictions on investment and in 1950 we joined the U.S.A. in fighting the Korean War. (See notes in posts 31 and 53 by Poggy1156 for more on these situations).
2. Within a 30 year period (1914 - 1945), the railways had been sacrificed twice to help Britain survive two World Wars.
Perhaps there's even a book here if somebody cares to write it?
At the cessation of the First World War (1914 - 1918), the railways should have been Nationalised to help provide the Country with a better, unified transport system. And they would have been as both the majority of both the public and political opinion was in favour in 1918 (see other topics on the Grouping for details), until the Strike of 1919 changed the governing political stance. (Lloyd George and Eric Geddes had already begun to set up many of the necessary functions for a unified network in a government dept, the A.R.L.E. had drafted a set of standard designs, etc.).
The U-turn and resulting compromise contained in the 1921 Act created the 'Big Four' conglomerates, which made the best of the 'controlled' railway situation. Eventually the four railway companies would give their all again during WW2.
3. By 1947, they were classed as "a poor bag of assets" in run-down condition; with many worn out locomotives and rolling stock, damaged infrastructure, massive maintenance arrears in all areas, speed restrictions on many sections of permanent way, dirty and unkempt buildings, etc. All due to over use and under maintenance throughout the war years.
4. The Transport Act of 1947 created a Nationalized railway network. British Railways was a huge organisation: in round figures, 50,000 track miles, 20,000 route miles, 6,700 stations, 20,000 steam locomotives, 40,000 coaches, over a million goods wagons and 625,000 employees. Plus there were 20 engineering works, hotels, ports, docks and ships and thousands of road vehicles, etc.
5. Because of the way the British railway companies had evolved, in-house manufacture of most of their transport connected requirements was also the norm. This was unusual (world-wide) and whilst being good for local employment was not the most efficient way for the country to produce the locomotives, wagons, coaches, etc. for its railway network.
Being first in the railway industry had not produced the ideal, or the most economical methods and/or standards as a whole.
6. Neither had being first produced the ideal network for the British Isles. 'Laissez-faire' Victorian Governments had encouraged rampant competition, producing a spiders web of duplication and just too many lines for two small islands. Many had been built to different standards; local and territorial economics imposing different restrictions on loading gauge, axle loadings, etc.
7. As early as WW1, all competent railway engineers knew that electricity was the most effective and economical power for concentrated networks in industrialized nations and could increase line capacity by up to 30% (Riddles knew this from his days as an apprentice).
But the initial infrastructure installation cost for electricity was high and between 1923 - 1947, only one of the Big Four companies had been in a position to take the bold step of employing a co-ordinated electricity programme (The Southern under the leadership of Sir Herbert Walker) .
The Government sponsored Weir report of 1931 had said electrification was the railways' 'holy grail', but did not suggest a practical way of achieving this benefit. Plus, after the slump, there was no money available for the significant installation costs, although capital was put into other projects.
8. As the head of the Electrical & Mechanical division within the newly formed British Railways (with responsibility for the largest share of the total workforce of 625,000 employees - split between operations and manufacture), Robert Riddles first task on 1st January 1948 was to keep the country's unified railway network running without incurring significant extra costs.
Next job, to begin to build a team of people who could work together for the common good and common goals of the newly created organisation. High ideals in a Britain deep in austerity measures; borrowing to the hilt to stay afloat and imposing restrictions on investments.
9. By 1948 (as Jonny points out), the diesel engine had been around for some considerable time and was in the process of rapidly replacing steam locomotion in the western and central railways of the U.S.A. However, it was not the economic first choice for the British railway network, with over 90% of operations and infrastructure designed to be provided by steam locomotives.
Diesel-electric power worked well over long distances of the western U.S.A., with light-weight consists and by 1948 the conversion to diesel was well under way west of Chicago. Undeniably the Class A roads could stand the high capital costs per unit and balance the economics of greater time in traffic and minimal infrastructure changes against eventual profit returns.
However, immediately post-WW2, diesel power was not the only choice for all the eastern U.S. roads, where coal was cheap and some electric power already working alongside the latest steam engines. (Peach) James refers us to the 1947 reports, where the latest NYC locomotives were used on intensive schedules and came very close to the running costs of the comparative diesel units - but at around one third to one half of the capital cost per equivalent horse-power unit.
Both the NYC and PRR had plenty of experience with electricity and the Norfolk & Western owned its own mines, so the economics of dieselization were not so clear cut.
10. Many areas of the British Isles virtually 'floated' on coal seams and in 1948 all our crude oil was imported. Logic suggests that it was better to use our own raw materials and organise production within the nationalised framework, rather than import oil, over which we had little control of production or price. (An experiment in 1947 on a few steam locomotives was soon reversed).
If you've got this far, those are some of the raw facts and hard economics facing the U.K., the railway network and Robert Riddles as he accepted the new job in 1948.