The largest of the 'big four' companies created by the Railways Act of 1921 the London Midland and Scottish Railway (LMS) was formed on 1 January 1923. The major constituent companies were the London & North Western, running the West Coast route from London to Glasgow, the Midland Railway which served the same destinations but via the highly scenic Settle and Carlilse line, plus a number of large regional companies including the Lancashire & Yorkshire.
The combined company was a vast undertaking with numerous interests other than railway operations. It was the largest company in the British Empire and the United Kingdom's second largest employer, after the Post Office, having a larger staff than the British Army! The LMS also claimed to be the largest joint stock organisation in the world. In 1938, the LMS operated 6,870 miles of railway.