Staff at Wiltshire Heritage Museum got a shock on Friday when they got a demand for £4,500 from Wiltshire Council.

The bill came out of the blue as the museum, a registered charity, has enjoyed exemption from business rates for years.

They also get £36,000 grant aid from Wiltshire Council, about a seventh of the museum’s running costs, and will now have to hand back nearly 12 per cent of that.

The demand has been backdated to April, the start of the financial year.

Doug Roseaman, museum trustee, said: “The letter said this change of policy was made last October but we knew nothing about it.

“We work to a very tight budget and it will be very hard to find this money.”

Wiltshire councillor for Devizes Stuart Wheeler said he would investigate.