A £35 million plan to revamp Poole’s St Ann’s Hospital gets underway this autumn after getting the green light from the borough’s planners.

The first phase to upgrade the hospital for people with mental health problems for Dorset HealthCare University NHS Trust is expected to be completed by summer 2013, with subsequent phases to follow.

It involves the refurbishment of a 1980s block and two new buildings designed by Nightingale Associates, sharing the cliff-top with the Grade II-listed, 100-year-old former sanatorium building.

The first building to be constructed will be an extension to the existing 1980s building, providing a new acute assessment unit and male treatment ward accessed through a three-tiered shared canopy entrance.

The original building will be refurbished to provide single en-suite bedrooms. The second new building will have 32 single bedrooms and support facilities.

“Considerable time and effort was invested by the client and design team for the pre-consultation planning meetings as our design required a sensitive intervention between the old and the new,” said project architect Graham MacDougall.

“By using timeless architectural language and materials we believe as a team we have created an exemplary scheme that will benefit all building users.”

Bed numbers will increase by only one from 107 but people with mental health problems will be treated in a modern setting with improved facilities.

The plans were backed by two celebrities, Karen Hardy, former Strictly Come Dancing star who spent her childhood in Dorset and suffered post-natal depression, and comedienne Ruby Wax, who has highlighted her battle with depression.

A masterplan was developed by Nightingale and Terence O’Rourke Ltd, whereby the central open space will be reconfigured to reflect the 1900s plan, complementing the original historic vision.

The three-tiered entrance features large expanses of glazing to maximise daylight and the surrounding views of the site, which overlooks Flaghead Chine.