They are, to quote Mark Knopfler, down in the tunnel trying to make it pay. Transport for London has this week been holding auditions for buskers, assessing the performers for licences that allow access to pitches on the Tube and, for the first time, the Elizabeth line. It’s a bureaucratic approach to a traditionally informal activity, but passengers will get their tunes and buskers will get their money.

Knopfler wrote his Dire Straits hit ‘Walk of Life’ after seeing a photo of a busker turning his guitar towards the subway wall to improve the echo. It’s the sort of attention to detail you need. Busking is the ultimate ‘give the audience what they want’ test – forget artistic merit, you have to entertain. Succeed and you eat, fail and you don’t.

These days performers have card readersbut 30 years ago, when I was a busker, cash was king. Watching a pound coin land in your guitar case feels great; the odd fiver even more thrilling. My record was £90 in 20 minutes outside the Albert Hall after an Eric Clapton gig. Ninety quid in change is reassuringly weighty. I have since done work that was better paid, but I’ve never felt as rich.

In those days anyone could turn up and have a go. Tube pitches worked an hour at a time, buskers booking slots via a handwritten list on the nearest advertising poster. Occasionally someone would get moved on and a new list would start, but almost every staff member who had been told to shift you would murmur ‘just go round the corner for a couple of minutes and then come back’.

Once in a while, British Transport Police would take your name. Get caught too often and you’d end up in court. That happened to me only once. The magistrate at Great Marlborough Street read my written statement. ‘You say you started busking to pay your way through university. What did you study?’ Economics, I told her. ‘That figures,’ she replied, and fined me £20.

Some famous names developed their skills as buskers. George Michael treated Leicester Square passengers to ‘Candle in the Wind’ and songs by Queen, while Rod Stewart branched out from the same station to Brighton, then Paris and Barcelona. He was finally deported from Spain for vagrancy.

Others have busked after stardom called. Paul McCartney did it for a daydream sequence in his 1984 movie Give My Regards to Broad Street, imagining how he would fare if his career collapsed. It was filmed outside Leicester Square Tube and despite Macca’s only disguise being a pair of sunglasses, no one recognised him during an up-tempo version of ‘Yesterday’. ‘God bless you squire… thank you ma’am,’ he intones as the money is dropped. He later recalled that ‘this fabulous drunk Scotsman, who didn’t know me from Jesus, came up, threw his arm around me and gave me all his coins’.

Sting had the same fear for real. Heading down into the Tube, he pulled a hat down over his eyes, made £40 and was ‘over the moon’. A woman thought she recognised him, but the man behind her told her not to be so stupid – what would Sting be doing busking? ‘He’s a multimillionaire.’