In May 2003, London Underground won the right to change the laws and the bylaws to make busking legal on the Tube.
Starting as a 16-week trial, the scheme has gradually expanded. The initiative now involves more than 356 buskers entertaining the network's millions of commuters on 30 pitches in 22 stations.
Steve Lewis, contracts manager for advertising and sponsorship, said: "The scheme in collaboration with Carling has been very successful. It will remain managed in house until a suitable sponsor is selected to help this unique and successful initiative to keep on flourishing and developing.
"LU is also working in collaboration with CBS Outdoor, LU's advertising contractor, to seek sponsorship."
"The London Underground busking scheme was originally implemented as a result from customer demand for talented musicians to be licensed to perform on the Underground. London Underground's passengers have made this scheme a success through their generosity and support of the buskers who are not paid to play on the Underground."
In June last year, CBS Outdoor -- then called Viacom Outdoor -- retained the £800m advertising contract for the London Underground.
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