It was created in 2002 by a merger between Brent, Kensington & Chelsea and Westminster Mental Health NHS Trust, Harrow and Hillingdon Healthcare Trust, and the substance misuse service component of Hounslow and Spelthorne Community and Mental Health NHS Trust.

It subsequently won additional contracts, including Milton Keynes Community Health Services from April 2013.

The intention was to achieve pay bill savings, by recruiting new staff on less expensive non-NHS contracts.

[3] It was named by the Health Service Journal as one of the top hundred NHS trusts to work for in 2015.

At that time it had 5745 full-time equivalent staff and a sickness absence rate of 3.51%.