Running between Walthamstow bus station and North Woolwich, it is operated by Arriva London.

On 21 July 2023, a consultation for route SL2 was opened by Transport for London, and closed on 4 September the same year.

[1][2] It was awarded on 20 October 2023, and was introduced on 2 March 2024, using existing Alexander Dennis Enviro400H Citys.

[3] It is operated by Arriva London as a variation to its route 123 contract that it parallels between Walthamstow and Ilford.

[6] From June 1996 until August 2002, a previous route SL2 ran in Central London, connecting the mainline railway stations at Paddington, Marylebone, Euston, St Pancras, King's Cross, Liverpool Street, Fenchurch Street, London Bridge, Waterloo and Victoria.