[2][1] On completion of his apprenticeship, he spent a year as a fitter at Sharp Stewart in Manchester, before returning to the GSWR drawing office at Kilmarnock; he later became works manager.

[1][2] Patrick became the Locomotive Superintendent of the GNR from 1 October 1866),[3] At the end of June 1878 he left the GSWR for the South Eastern Railway.

[5] Like his brother, James Stirling favoured the domeless boiler, known as the "straightback" and cabs for the enginemen.

[2][4] Although not the first British locomotive engineer to use the 4-4-0 type, he was the first to produce a 4-4-0 which could be regarded as successful, with his G&SWR 6 Class of 1873.

[2][6] On the South Eastern Railway, Stirling designed just six classes of locomotive in his twenty years – three of these were of the 4-4-0 type for express passenger work, each more capable than the last; his other three classes were an 0-6-0 for goods, an 0-4-4T for suburban passenger, and an 0-6-0T for shunting.