At the age of twenty, Harrison became a clerk on the London and North Western Railway (LNWR) at Shrewsbury. He rose through the ranks, working at Euston under George Findlay, the General Goods Manager; a later post was that of Assistant District Superintendent at Liverpool, and in 1874 he moved to the equivalent job at Chester. He remained there for a year before, aged 31, becoming Assistant Superintendent of the Line. Ten years after this he was appointed Chief Goods Manager of the LNWR. His next promotion was in 1893, when he became General Manager of the LNWR, a post he held until the end of 1908. The following year he joined the Board of the South Eastern Railway, very soon becoming Deputy Chairman, and also being appointed to the South Eastern & Chatham Railway Companies Joint Managem