A 21-year-old man has been arrested after a man was set upon by a group of thugs and attacked outside a pub.

The incident happened shortly after 10pm on Tuesday at the Holland Tringham pub on Streatham High Road.

Police said a group of four or five men, believed to be predominantly Eastern European, were drinking in the pub but were asked to leave by staff.

They were then seen running along Streatham High Road following an alleged attack on a 48-year-old man on the pavement outside.

A spokesman for the London Ambulance Service said they sent one ambulance crew to the scene and a man was taken to hospital.

He was released after being treated for head injuries, police said.

Passerby Stephen Anderson saw a blue transit van in the road and two people leaning over a man lying on the pavement.

He said the attack had left the man’s skull “virtually caved in” and said his girlfriend had assisted staff from the Wetherspoons pub with providing first aid.

“I noticed a massive amount of blood in the road,” he said. “The man was mumbling, and his body was shaking.

“When the police and ambulance arrived my girlfriend and I left the scene, as we had not witnessed the attack.

“My girlfriend was shaken as she said that the back of the victim’s skull was virtually caved in.”

Police are appealing for witnesses. Anyone with information should call Trainee Detective Constable Nicki Pendry on 020 8649 2039, email Nicki.Pendry@met.police.uk or speak to Crimestoppers anonymously on 0800 555 111.