A schoolgirl from South Norwood told a gay barman she was making a documentary on happy slapping' before she filmed him being kicked to death on her mobile phone, the Old Bailey heard.

Six youths, including the girl, laughed as they then watched the footage of David Morley's attack while the 37-year-old lay dying in hospital.

The girl, then aged 14 who cannot be identified for legal reasons, is said to have approached Mr Morley and his friend Alistair Whiteside as they sat on a bench on central London's South Bank on October 28 last year and told them: "We're doing a documentary on happy slapping."

Her 17-year-old accomplice admitted starting a fight with Mr Whiteside while Mr Morley was attacked by other gang members.

The teenager, who cannot be identified for legal reasons, also admitted taking part in other attacks on the same night.

The gang then went back to a block of flats in Kennington and watched the girl's video clips. The 17-year-old said: "At the time I thought it was funny."

He admitted he lied when he was interviewed by the police because "I didn't want to be involved in an incident where someone died."

Reece Sargeant, 21, Barry Lee, 20, and Darren Case, 18, deny murder together with the two 17-year-olds and the 15-year-old girl.

They also deny conspiracy to cause grievous bodily harm with intent and conspiracy to rob between October 28 and 31.

The trial continues.