Running between North Finchley and Walthamstow bus stations, it is operated by Arriva London.

[3][4][5] It is operated by Arriva London as a variation to its route 34 contract that it parallels between New Southgate and Walthamstow.

[6] After a competitive tendering process, the contract was retained by Arriva London from November 2024 with the Alexander Dennis Enviro400H Citys to be replaced by brand new BYD BD11 Electrics.

[10] Route SL1 has been criticised for not offering a direct link to North Middlesex University Hospital in Edmonton.

[11] From June 1996 until August 2002, a previous route SL1 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.