It should be pointed out that the following individuals were in overall charge of the design offices of the LMS, and that their subordinates often contributed heavily to the designs produced.
George Hughes (born 1865, died 1945, CME 1923-1925)
At the grouping Hughes was the CME of the combined LNWR and LYR and was given the job of CME of the LMS. He had designed various types of locomotive and was one of the British pioneers of firetube superheaters. During his short tenure as CME he attempted to resolve the LMS's problem with underpowered locomotives, but only his mixed traffic 2-6-0's were actually built, and that occurred after he retired.
(Sir) Henry Fowler CBE (born 1870, knighted 1918, died 1938, CME 1925-1930)
The son of an Evesham cabinet maker, Fowler apprenticed at the LYR before joining the MR, eventually becoming the CME to that company, although he was seconded to various advisory posts during World War I, for which he received the CBE in 1917 and was knighted in 1918. Fowler's main contributions were towards improved production methods and metallurgical improvements in locomotives, but it was here that his battle to overcome the MR "Small Engine" policy began, a battle that would continue until 1930. With the formation of the LMS, Fowler became Deputy CME to Hughes, before replacing him in 1925.
Fowler's tenure was dogged by the problems associated with standardising the locomotives that the LMS had inherited from the companies that formed it, and the persistent problem of underpowered locomotives, most notably the ones inherited from the MR. Although he was able to develop some of Hughes's designs, his own designs for more powerful locomotives were rejected by the motive power due to the fact that operating them would require larger turntables. His "Royal Scot" engines were accepted, and were at least a step in the right direction, although this design was later overshadowed by the Stanier "Princesses". His tenure as CME ended in 1930, when the LMS promoted him into a research position.
Henry Fowler has at least been commemorated in his home town with a road named after him, and a blue plaque mounted on the former Midland Railway Station building.
Ernest J H Lemon (born?,died?,CME 1931)
Contrary to popular belief (and most texts), it appears that Ernest Lemon held the post of CME during 1931, after Fowler was transferred to the LMS' s Research Department. It appears that Lemon was acting purely in a holding capacity, and apart from pushing through a couple of Fowler's last ideas, he did not produce any new designs. No 1944 locomotives are credited to him, but since the 1944 ABC doesn't recognise them as a CME anyway, there is the possibility that it may be in error. Unfortunately, Lemon has no entry in "The Oxford Companion to British Railway History" which means I still have very little information on him.
(Sir) William Stanier (born 1876, knighted 1943, died 1965, CME 1932-1942, Consultant 1942-1944)
At the age of 16, Stanier joined the Great Western Railway where he worked under William Dean and Charles Collett. On becoming CME to the LMS in 1932, he set about trying to finally solve the problems with locomotive power, and perhaps it says a lot for Stanier that he finally succeeded (although it should be mentioned that he did build on ideas that his predecessors proposed). By 1947, over 2,000 locomotives had been built to his designs, which often combined LMS features (e.g. outside Walschaersts Valve gear) with GWR features (e.g. tapered boilers). His crowning glory must be the "Princess Royal" and "Princess Coronation" class locomotives, but he also introduced diesel-electrical shunters and built a prototype diesel hydraulic 3-car passenger locomotive. He also built "Turbomotive" a single turbine powered locomotive based on a standard "Princess Royal" design.
In 1942, Stanier became an advisor to the Ministry of Production, and although was nominally CME until 1944, Charles Fairburn took over most of the responsibilities of the office at this point.
Charles Fairburn (born 1887, died 1945, Acting CME 1942-1944, CME 1944-1945)
Fairburn was more of an electrical engineer than a mechanical engineer and his short term as CME reflected this. Having studied under Fowler at Derby, he joined the LMS in 1934 as chief electrical engineer, becoming Stanier's deputy in 1937. His tenure saw the introduction of diesel-electric shunters (proposed by Stanier) and he initiated the design of a 1500hp diesel-electric locomotive. He also contributed a modified 2-6-4 steam tank engine. His premature death in 1945 perhaps robbed the railway world of someone who could have equaled (or even bettered) his predecessor.
Henry G Ivatt (born ?,died? CME 1945-1947)
Apprenticing on the LNWR from 1904, Ivatt, found himself working for the North Staffordshire Railway as Deputy Locomotive and Carriage and Wagon Superintendent after World War One. After the grouping Ivatt found himself as a special assistant to Fowler at Derby, where he undertook to improve the efficiency of locomotive repairs, managing to cut the numbers of locomotives under repair at any one time from 150 to 60. Stanier's arrival saw him take up the post of Mechanical Engineer, Scotland in 1931, but by 1939 he was assisting Stanier at Euston. World War II saw Ivatt involved with American locomotives shipped over to aid the war effiort, and their labour-saving devices would be used in his post-war designs.
The sudden death of Fairburn in 1945, saw the unexpected elevation of Ivatt, to the post of CME. Although only acting CME initially, he was eventually given the job permanently after Stanier gave the LMS board his whole-hearted support. Most of his work centred on improving existing designs, but between 1945 and 1947, he designed 3 new classes of steam locomotive for light to medium use, as well as producing the first mainline diesel locomotives, the project initiated by Fairburn.
Ivatt continued working as CME for the Midland Region of British Rail until 1951, the last of the "Big Four" CME's at nationalisation to retire.
[for some reason the Oxford Companion to British Railway History doesn't give him an entry]