Ronnell Dennis, aged 26, absconded from a mental health ward at the Riverside Centre in Hillingdon at around 17:00hrs on Sunday, 1 March.
Shortly before he left the hospital, another patient was assaulted – this patient was left in a critical condition.
Police are increasingly concerned for Dennis’ welfare and believe he may pose a significant risk to the public.
He is black, around 6ft 2ins tall and of a proportionate or athletic build. At the time of his disappearance he was wearing black clothing and a black bandana.
He has links to north and west London, as well as the Home Counties.
Dennis was last seen in the Chalk Hill Estate in Wembley at around 22:15hrs on Sunday evening.
Anyone who sees him is asked not to approach him but to call 999 immediately, quoting a reference of CAD3532/2MAR2020
Superintendent Duncan Slade, from West Area CID, said: “Dennis may be suffering from a mental health crisis and could behave in an unpredictable manner.
“If you have seen him since Sunday, 1 March or know of his whereabouts please do not approach him but dial 999 immediately.