In 1848 the LNWR opened their line from Leighton Buzzard to a terminus at Dunstable. Having failed to persuade the LNWR to extend the line to Luton, the Great Northern Railway was petitioned to provide a link to the town. This petition was unsuccessful so a number of wealthy landowners and the MP for Hertford promoted the Luton, Dunstable & Welwyn Junction Railway which would run from Dunstable where a connection would be made to the LNWR through Luton to Welwyn where there would be a junction with the Great Northern Railway. It was then intended that the cross country line should continue on to Hertford with a bridge over the Great Northern Railway line at Welwyn but the GNR objected to a bridge and the line never went ahead despite some work being started.

Two separate branch lines were then proposed, the Luton, Dunstable & Welwyn Junction Railway and the Hertford & Welwyn Junction Railway which opened on 1.3.1858 with intermediate stations at Hertingfordbury and Cole Green with a terminus at Hertford (later renamed Hertford North). With the Luton, Dunstable & Welwyn Junction Railway in financial difficulties it eventually amalgamated with the Hertford & Welwyn Junction Railway forming the Hertford, Luton & Dunstable Railway. The Hertford branch was absorbed into the Great Northern Railway on 28th June 1858.

Both branches initially ran into temporary wooden platforms at Welwyn (where Welwyn Garden City Station now stands). On 1st September 1860 the temporary platforms were closed with trains on both branches running into Hatfield. When a new through station at Hertford North opened in 1924 the earlier branch terminus at Cowbridge became redundant and was closed to passengers although it continued to handle goods traffic until 23rd May 1966 as there were no goods facilities at the new station.

Two further halts, Attimore Hall Halt and Hatfield Hyde first appeared in the public timetable in May 1905 but closed a few months later on 1st July 1905. A siding at Attimore Hall remained in use until 4th May 1964.

After closure in 1951 the branch was used for the location of a number of films until the track was lifted in July 1967.

The 6.5 mile Cole Green Way cycle and bridleway which between Welwyn Garden City and Hertford now follows the course of the line.

For further reading see Hertfordshire's lost railways by Keith Scholey ISBN ISBN 1 84033231 X

See other stations on this line Hertford North, Hertingfordbury, Cole Green and Attimore Hall Halt (Click on station)