When Damien Egan, the mayor of Lewisham, in south London, reviewed his borough’s statistics on drug arrests last year he felt a deep sense of frustration. Some 1,800 people had had proceedings brought against them for drug possession between 2016 and 2020, more than one a day. Ninety per cent were for possessing cannabis, with young black men disproportionately represented.

The system, as he saw it, was broken. “It just isn’t working,” said Egan, 37. “It puts so much emphasis on the police trying to solve the problem, but it’s clearly not working for young people. Things are difficult enough for young people to succeed in London as it is. Trying to do that with a criminal record is only going to make your life