A Royal Marine and his father have been stabbed on their doorstep as they tried to stop a group attacking a female family member in south London.

Matthew Stevenson-Webber, 24, was stabbed in the back trying to protect his sister in Mitcham on Tuesday night. He is in a stable condition.

His father Craig Joseph-Webber, 45, was stabbed in the head and is in a critical but stable condition.

A police spokesman said five teenagers, aged 17 to 19, had been arrested

A third man, aged, 30 was stabbed in the shoulder and is also in a stable condition in hospital.

Heard screaming

The family of the marine had contacted their MEP Nirj Deva on Wednesday about the incident.

A spokesman for his office said the men had heard screaming outside their home and went to help their relative.

They were then attacked by the group.

A Metropolitan Police spokesman said officers had been called to an altercation involving a group of youths in Belgrave Road at 2320 BST.

He said three men, aged 24, 30 and 45, were found suffering stab wounds and taken to hospital.

Five males, three aged 19, one aged 18, and a 17-year-old, have been arrested and remain in custody at a south London police station.