A GROUNDBREAKING thermal imaging survey has revealed the secret world of a colony of bats residing inside the deserted rooms of Blenheim Palace's Grand Bridge.

Staff at the Woodstock world heritage site commissioned the survey ahead of a multi-million-pound restoration project for the bridge, which was designed by 18th century architect and playwright John Vanbrugh.

It was known that bats were inhabiting the bridge, but the survey was able to determine more information about the protected creatures – including the precise locations of the roosts and details on the species of the bats.

The palace's historic buildings and conservation surveyor, Richard Bowden, said: “We knew the bridge was being used by bats during the summer months but we weren’t sure exactly where they were roosting, how many of them there were, how long they were spending there and also what species they were."

The bridge, which is believed to contain up to 33 rooms, including a boathouse and a bathing house, was partially submerged as part of Lancelot ‘Capability’ Brown’s grand re-design of Blenheim’s lakes and parkland.

A team of scientists from leading independent ecological consultancy, BSG Ecology, were brought in to carry out the survey using a combination of high-specification thermal imaging cameras and bat echolocation detectors.

In addition to a Daubenton’s bat colony, all three UK species of pipistrelle were recorded foraging over the lake.

Daubenton’s bats are one of 18 different bat species found in the UK.

They are particularly associated with lakes and rivers.

Like all bat species, their breeding sites and resting places are fully protected by law and so it was vital for Blenheim Palace to find out as much as possible about their movements and habits in order to safeguard them.