closed to passengers on 7 September 1964 and to freight three months later. Electrification first came in the early 1960s under British Rail in sections. Electrification to Chingford included the Stratford – Lea Bridge – Hall Farm Junction section (although this was never completed), and the line from Liverpool Street to Broxbourne via Seven Sisters and the Southbury Loop was electrified. The route via Tottenham Hale was still operated by diesel traction, the British Rail Class 125 'Lea Valley' DMUs. The line from Clapton Junction (on the Chingford line) through Tottenham Hale to Cheshunt and from Broxbourne to Bishops Stortford was electrified on 9 March 1969 and from there to Cambridge in 1987. Stratford to Coppermill Junction was electrified in 1989. The power supply is 25 kV AC overhead line. In 1991, a single-track branch line to Stansted Airport was opened, and services to London Liverpool Street commenced. In early 2011, ticket barriers were installed at , , Broxbourne, Cheshunt and Hackney Downs, some of the busiest stations on the line, to reduce the need for ticket inspectors on the Stansted Express service and reduce fare evasion. In May 2015, services from to , and via transferred to London Overground, along with a new station opening at . In August the same year, a direct covered walkway opened between and on the North London Line. In September 2019, the Lea Valley Rail Project was completed between Lea Bridge, and the new station at . This removed the level crossing at , and added a new third platform for both there and , along with a third track. As a result of the new and , platform extensions are necessary at many stations to allow for ten/twelve car trains to stop at stations respectively. However, the class 720 has selective door opening, allowing for some platforms not having to be extended. Services Services from Liverpool Street to Cambridge, Hertford East and Stansted Airport are operated by Greater Anglia. Express services from Liverpool Street to Stansted Airport are operated by Stansted Express, a sub-brand of Greater Anglia. Services from Stansted Airport to Cambridge (and onward to via ) are operated by CrossCountry. The line is part of the Network Rail Strategic Route 5, which comprises SRS 05.01 and part of 05.05. It is classified as a London and South East commuter line. In London, the line forms the Tottenham Hale branch of