Three males attempted to rape a schoolgirl as she was walking home from school.

The Metropolitan Police says it is investigating the attack in East Finchley, which occurred on Wednesday, October 7, around 5.30pm.

The force says the girl, 15, was walking home from school when she approached an alleyway off The Causeway and noticed three males smoking.

The males followed her before grabbing her and holding her against a wall, police said.

One of them sexually assaulted her and then pulled his trousers down.

The attackers were then disturbed by a man and they ran off down the alleyway, police said.

The man walked the girl to East Finchley station where he saw her onto a bus.

Police say they would like to talk to the man as he could hold information to help identify those involved – he is described as a white man, aged approximately 40, of slim build and wearing sports trousers.

He was carrying a blue bag and looked like he may have been going to the gym.

The suspects are described as black males, aged in the mid-to-late teens and wearing black school trousers.

One is desbecribed as having a slim build, with black plaits in his hair, approx. 5ft 11inches tall and wearing a navy blue Nike coat.

Another also has a slim build, with black wavy hair, approx. 5ft 7inches tall and wearing a black Nike coat.

Police say a third suspect is of chubby build, with dark curly hair, approx. 5ft 7inches tall and wearing a black Nike coat.

Police are appealing for information and witnesses.

PC Mary Fenton of the North West Safeguarding Team said:“I would like to reassure the community that these types of incidents are extremely rare and my team and I are working on all lines of enquiry to identify those responsible.

”In this incident, thankfully a passer-by intervened, stopping the attack, and I would ask him to come forward and speak to police – he could hold crucial information that could assist us.”

Anyone that can assist police in this investigation is asked to call 101 or tweet @MetCC and quote CAD6007/9Oct. Alternatively, contact the independent charity Crimestoppers anonymously on 0800 555 111.