Sir Paul McCartney raised eyebrows as he left a charity event with a mystery brunette balanced on his knee.

Sir Paul, 65, giggled as the woman perched illegally on his lap as the couple were driven away from a party at Great Ormond Street Hospital.

The former Beatle and his pal squeezed into the front seat of his people carrier, after the star made a surprise appearance at the London hospital's annual Christmas party.

The pair certainly looked cozy despite the cramped condition, but pals of the music legend — who has been linked to actress Rosanna Arquette in recent weeks — insisted the mystery girl was not his latest love interest.