A prisoner serving a five year sentence for robbery at Feltham Young Offenders’ Institution has escaped during a mental health assessment in West London.

Ashley Waterman absconded after being taken from the institution in Bedfont Road, Feltham, to a secure unit for tests.

The 21-year-old was jailed after pleading guilty to robbing a branch of McDonald’s in Finchley Road, Camden in April 2007.

Staff at the unit reported him missing at 1am on Saturday.

Waterman is described as dangerous by police who say he should not be approached.

He is white, 5ft 8in, of slim build, with short light brown hair, and has connections in Paddington, west London.

Anyone with information should contact Crimestoppers on 0800 555 111.