A man punched and racially abused a Good Samaritan on a bus at Heathrow Airport before bizarrely doing chin-ups, police said.

CCTV images released by police show the man using a handrail to carry out the gym moves after hitting a woman in the face on the 423 bus.

The woman was on her way home from a night shift at 6.15am and had earlier intervened to stop the man abusing another woman at a bus stop, a Metropolitan Police spokesman said.

"The bus arrived at this point and when the victim, who is of Polish descent, boarded it the suspect followed her on to it. He continued to racially verbally abuse her before punching her in the face," he said.

"The victim ran off the bus whilst the suspect remained on it and got off in Hounslow. He was captured on CCTV on the bus and is seen doing chin-ups after the assault."

Police released images of the February 25 attack today and appealed for help to find the attacker.

He is described as being a light-skinned Asian man with "untidy stubble". He is approximately 5ft 9in and of medium build.