Sir Mick, 82, was seen performing the traditional song Handsome Molly with his fellow punters, a track that was also on his Wandering Spirit solo album in 1993.
Commenting on the surprise show, Johnnie at the pub said: “The Half Moon prides itself on its authentic atmosphere and welcoming community.
“Our Sunday folk session has been going for many years and is open to everyone – whether you’re a beginner player or an international rock star.
“You never know what to expect at the Half Moon.”
Sir Mick last performed with the Rolling Stones in 2024 as part of the Hackney Diamonds Tour.
The band’s new album Foreign Tongues, their 25th, will be released in July.
