The Cassel Hospital, set in a Grade II listed building on a prime site overlooking Ham Common, could be set for redevelopment – possibly including affordable housing.

The psychiatric facility which is run by the West London NHS Trust is said to be 'under-occupied', despite evidence of a surge in mental health issues.

At the same time, the Trust has indicated that the historic building is expensive to run due to 'significant maintenance challenges and high costs'.

Separately, the new Local Plan drawn up by Richmond Borough Council has suggested that the site could be redeveloped, perhaps to include a mix of health, community and housing.

The plan indicated the site presents an opportunity to be converted into new community facilities if it is declared surplus to requirements by the Trust.

It says any development would be dependent on the Trust's decision on how much of the site it would need to keep - meaning the site could be completely or partially redeveloped.

The plan adds a residential-led scheme, with affordable housing, would only be considered if alternative social or community infrastructure uses had been explored and discounted. It says residential uses should be limited to the minimum necessary for the scheme to be viable.

The plan says: "If the site and hospital are declared surplus to requirements, social and community infrastructure uses are the most appropriate land uses for any development proposal. Conversion or potential redevelopment for residential uses could be considered if it allows for the protection and restoration of the listed buildings."

It adds: "Development would not be supported in the parts of site that are designated OOLTI [Other Open Land of Townscape Importance] and SINC [Sites of Importance for Nature Conservation]. Any future proposal would need to protect and where possible enhance the character and openness of the designated open land."

The expected implementation timescale of any redevelopment scheme if it went ahead, according to the plan, would be the medium-term - meaning within five to 10 years.

Cassel Hospital treats people with severe and complex personality disorders. The site covers 3.97 hectares and includes buildings up to three storeys tall, with some listed.

The Local Plan will go out to consultation for six weeks starting in May, under Regulation 19 of the Town and Country Planning (Local Planning) Regulations 2012, if approved by the environment committee and council this week, after any final minor changes.

It is expected to be submitted to the secretary of state for examination later this year for adoption in winter 2024 or 2025. Once adopted, it will shape development in Richmond over 15 years, guiding decisions on planning applications in the borough.

A statement from West London NHS Trust said: "The Cassel Hospital is a unique part of the NHS that provides therapeutic interventions to people with complex needs. We are in discussions with the Cassel's community of patients, service users, staff and supporters about refreshing the model of care in order to secure a future for the service whilst building upon its legacy.

"The current Cassel Hospital premises and grounds are treasured by the community, but are also under-occupied and with significant maintenance challenges and high costs.

"The trust has no confirmed plans to relocate the service or dispose of the premises, but we are looking into all options in order to ensure that we provide care in a modern, fit for purpose and safe environment."