Sir Tom Jones continued the Arthur's Day celebrations with a musical performance at London's Senate House.
Earier punters at The Wheelbarrow pub in Camden had tried not to spill their drinks in surprise when the Welsh music legend popped into the London venue for an unexpected gig.
The Delilah singer sang to a crowd of just 100 people who were celebrating Arthur's Day, in recognition of Arthur Guinness, who established the Dublin brewery for the Irish drink that takes his name.
In 2009, when Guinness celebrated its 250th anniversary, a series of musical performances were commissioned to mark the event and the tradition has continued.
Tom tweeted "The Wheelbarrow in Camden has well and truly been rocked! Thanks all for coming" before heading to the official Arthur's Day party, he was already known to be headlining, at the capital's Senate House Building.
The party, which was one of a number taking place across 55 countries, also featured performances from with Wretch 32, VV Brown and Razorlight and was streamed live on YouTube.
The 72-year-old seemed to enjoy the celebrations all round, tweeting again "A fantastic crowd, big fun at Senate House, to Arthur! - thanks Guinness and everyone xx"