He must have felt very alone, underneath the huge domed roof of the doomed Roundhouse - so for the first 15 minutes, he kept his head down, and ploughed through the oldies. "We didn't know how many people would remember who I was," said Bragg, explaining why his return to the London stage was a one-off and solo. He needn't have worried, the place was sold out and when he forgot the words of "St Swithin's Day", the audience sang them for him. He raised his game with an absorbed, passionate rendition of "Levi Stubbs' Tears". "Yes!" he bellowed as the last chord rang out. "I don't forget that bugger, I can tell you." He gave us poetic songs of broken love. He gave us socialist anthems with folk tunes, and funny stories. He gave us a headache with his Clash-like guitar sound. And he gave us a history lesson, as the preamble to "A Pict Song", a new one with words by Rudyard Kipling. First the Romans offered the Picts central heating, said Bragg; then roads ("and the people up in the trees shouted 'piss off'") and finally, persuasively, "capu-bloody-ccino". Ever since then the Italians have been beating us at football."
What a lad. Except these days he's a dad and the title of his new album is William Bloke. The difference? "A bloke doesn't need to drink 13 pints to prove himself. And you can borrow a ladder off him." And just to prove it, he came out for the first encore holding a ladder aloft.
Like every old mate you meet in the pub, he stayed around too long - and got a bit embarrassing, with a halting attempt to define a spiritual "socialism of the heart". But this indulgent audience didn't seem to mind; just having him around to sing "There is Power in a Union" seemed comfort enough. Together in the dark, singing along, it was almost possible to believe.