OMG! David Walliams exposes Mark Ronson’s bum!

David Walliams stripped Mark Ronson of his trousers in front of 3,000 people.

Mark didn’t know what he was in for when the comedian asked him to join him on stage for a sketch at the Concert For CARE event at the O2 Academy in Brixton on Monday.

An unsuspecting Mark looked mortified as David – in the guise of Little Britain character Des Kaye – then jumped him and exposed his bum.

‘When I put my mind to it, I have the strength of ten men so there’s no stopping me,’ the 38-year-old told the crowd.

‘You are going to get dry-humped by Des Kaye. He’s Rod Hull without Emu.’

Mark eventually managed to escape his clutches and later showed he wasn’t offended by the prank when he got back on stage to perform with Simon Le Bon.

‘Mark is a cool, calm character,’ David tells The Sun. ‘To put him in that position was out of his comfort zone.

‘I offered to buy him a new suit. He said it wasn’t necessary because he gets them free from Gucci.’