Transport for London

Transport for London (TfL) is an organisation that runs the public transport network in London. It is held with direct responsibility to the mayor of London.
Numbering of bus routes.
Historic numbering.
Historically, bus routes were grouped by the type of service that they provided.
The 1924 London Traffic Act used the Bassom Scheme. It was named after A.E. Bassom of the Metropolitan Police who made it. Changing and short lines used letter suffixes. Also, the numbers were grouped by the company that operated the route.
The numbering was changed in 1934 after London Transport was formed.
Current classification.
"*Except 607, which is a normal daytime route"