Original: During 1909-1922 the London and North Western Railway embarked on a project to electrify their London inner-suburban network , encompassing the lines from London Euston to Watford and the North London Railway from London Broad Street to Richmond , including branch lines such as Watford to Croxley Green ( where a depot was built to house the electric units ) , and links to what was to become the London Underground network .
Simplified: This also included branch lines such as Watford to Croxley Green ( where a depot was built to house the electric units ) , and links to what was to become the London Underground network .