A young lad was strumming a guitar in the subway, while his companion played a flute. Along came two policemen, and the first one asked to see their licence. The guitar player said something I did not hear, to which the police officer replied "Yes you do". At this point I left the subway, and do not know whether or not the buskers were arrested.
Now it appears that the law in the UK has changed, and that buskers no longer need a permit. You used to need a street entertainer licence, obtainable from your local authority. Nevertheless I recently checked the websites of four local authorities, and could not find any reference to busking permits. One site had a list of rules for buskers to follow, but made no mention of any paperwork being needed.