Thomas Heywood trained as a pupil with T. Hurry Riches at the Taff Vale Railway, and won a Whitworth Exhibition gold medal for engineering in 1899. His first employment was as a draughtsman and inspector at Cardiff. In 1902 he moved to Inseine in Burma to take up the post of Assistant Locomotive, Carriage and Wagon Superintendent of the Burma Railway. On his return from Burma, Heywood returned to the Taff Vale where he became the Junior Assistant Superintendent at Penarth Dock.
In 1914, Heywood moved north to become the Locomotive Superintendent of the Great North of Scotland Railway. Heywood's tenure overlapped with World War 1 which prohibited many new locomotive designs. However he did manage to significantly expand the use of superheating on the GNSR, and he created a new class of superheated 4-4-0s (LNER D40).
Heywood's post ceased to exist after Grouping (1923), and he became the LNER's Running Superintendent of the Northern Scottish Area. This post was initially based at Gorton, but he returned to Scotland in 1927. Heywood retired in June 1942, and he died in November 1953 at Aberdeen.