Police have appealed for information after an off-duty officer was knocked unconscious at Liverpool Street station.
The incident happened at the London station at around 12.30am on Friday 10 December, the officer noticed a man smoking at the bottom of the escalators.
The off duty officer then challenged the man who then closely followed him up the escalator also joined by 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, in his twenties, around 6ft tall and of medium build with short brown hair and a stubble. At the time of the incident he was wearing a dark jacket and jeans.
The other man is described as white, in his twenties, of medium build and with short brown hair. At the time of the incident he was wearing a navy puffer jacket and dark jeans.
Police have said that they want to speak to anyone who may have witnessed the incident, or anyone with information to further assist their enquiries.
Witnesses, or anyone with information, can contact BTP (British Transport Police) by texting 61016 or calling 0800 40 50 40 quoting reference 37 of 10/12/21.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.