An off-duty officer was knocked unconscious at Liverpool Street Station after challenging a man who was smoking inside, police say.

It was reported that the officer noticed a man smoking at the bottom of the escalators at 12.30am on Friday, December 10.

He challenged the smoker, who then followed him closely up the escalator along with another man.

The officer then woke up on the floor and was bleeding, with no recollection of what had happened.

The first man is described as white, aged in his 20s, around 6ft tall and of medium build, with short brown hair and a stubble.

He was wearing a dark jacket and jeans at the time.

The other man - described as white, in his 20s and of medium build, with short brown hair - was wearing a navy puffer jacket and dark jeans.

British Transport Police (BTP) want to speak to anyone who may have seen incident or has information that may assist their investigation.

Contact BTP by texting 61016 or calling 0800 40 50 40 and provide reference: 37 of 10/12/21.

Alternatively, call Crimestoppers anonymously on 0800 555 111.