After seven grueling miles, Mark McGowan pushed the nut up the steps to Prime Minister Tony Blair's Downing Street residence and told waiting reporters: "I've got a sore nose."

Performance artist McGowan -- nose shielded by a grimy sticking plaster -- deftly flicked the nut onto Blair's front step, and was greeted by an official who handed him a mug of tea.

The 37-year old has gone through 13 nuts during his grueling quest to highlight rising student debt.

"I'm trying to show the Prime Minister that he needs to bring back grants to people who need them," he told Sky television.

"I've got 15,000 pounds worth of debts -- and now I've got a sore nose," he added.

McGowan, who has previously walked for 11 miles with a turkey strapped to his head to persuade fat people to eat less, was unimpressed by the tea he received from the premier's office. "It was like a builder's mug -- you could see the stain on the inside," he said.

But the mug was nothing to some of the trials he has to endure during his stunt.

"The streets of London are filthy," he said. "There's human hair, bird poo and all sorts."