A patient being held at a secure psychiatric unit has gone missing.
Mr Zhen Li-Shen is not thought to be at risk to anyone
Zhen Li-Shen, 33, disappeared from Chase Farm Hospital, in north London, after failing to return from a walk in the grounds on Thursday.
Police say that Mr Li-Shen, a Chinese national, is of "an unknown risk to himself and others".
He has black hair, is of medium build, wears glasses and is thought to have contacts in a number of areas around north London.
The 33-year-old is also thought to have contacts in Walthamstow, east London, and in Northern Ireland.