After the mime artists and fire jugglers vacated the main piazza, John Fisher, a cash-strapped headmaster, took centre stage, in an attempt to raise pounds 50,000 needed to save a teaching post at his run-down school.
Faced with the fourth consecutive year of budgetary cuts, Mr Fisher, 49, of the Rush Common Primary School, Abingdon, Oxfordshire, decided it was time to take a leaf out of its students' books, and get a holiday job busking to raise finances.
He said: "Something had to be done if teaching standards are to be maintained. We are in a desperate situation and I thought it was time to raise awareness of the problem we face."
Pupils at the school are at present being taught in classes of between 35 and 40, under leaking roofs, in poorly decorated buildings which they cannot afford to repair.
But the first London appearance of the guitar and banjo-playing duo, called Paddy and Taff, did not go according to plan.
As the rain lashed down, passers-by rarely glanced from behind their umbrellas to watch the act. Their first gig in the capital brought in only pounds 5.10. Mr Fisher and his singing partner, Colin Miles, 50, who have so far raised pounds 600 on the first leg of their round-Britain tour, doubted they would reach their optimistic target.
"We have had a tremendous response from the public, who have said it is sad we have had to resort to this but, realistically, I don't think we'll raise pounds 50,000 - but the money has to come from somewhere," said Mr Fisher.
But all is not lost for the group, as their fan base has rapidly grown to include the likes of the Liberal Democrat leader, Paddy Ashdown.
After watching an earlier performance, Mr Ashdown said: "What kind of society are we living in when a headmaster has to spend his half-term busking to pay for a teacher? It is a joke that this is what Britain's education system has come to."
Another groupie, Celia Bowden, a bursar on a day-trip from Oxfordshire, said it was good to see people with a talent taking things into their own hands when all other approaches have failed.
Although the "Face The Music" tour continues to Nottingham, Durham, Newcastle, Liverpool and Coventry, Mr Fisher was not letting the group's sudden rise to fame get to his head.
He said: "We do enjoy playing and write a lot of our own material, but I don't think the Spice Girls have much to worry about.
"We are more a particular brand of `old spice' and cater for a very different kind of audience."Reuse content