An investigation has been launched after apparently unauthorised building work was carried out at a Grade II listed building in St Albans.

Herts Advertiser: The Marlborough Alms House works.The Marlborough Alms House works. (Image: Archant)

District council officers visited the Sarah, Duchess of Marlborough Almshouses in Hatfield Road on Monday, September 25, to inspect work being carried out by contractors.

The Herts Ad has been told officers deemed the work to be unauthorised and issued an immediate enforcement notice to stop any further building work.

The building is 280 years old, and was commissioned by Sarah Churchill (1660-1774), Duchess of Marlborough and wife of General John Churchill, first Duke of Marlborough. It was built in 1736, and the facade was restored in 1850.

Robert Hill, chairman of the buildings and estates sub-committee, said: “This was an accident waiting to happen; by employing unskilled contractors not working to a proper specification who clearly have no experience with listed buildings and conservation work.

Herts Advertiser: Duchess of Marlborough's almshousesDuchess of Marlborough's almshouses (Image: Archant)

“Our job as trustees is to protect and preserve this ancient historic building. This is what happens when you pay the lowest price.”

Tracy Harvey, the council’s head of planning and building control, said: “We are enquiring into an allegation that unauthorised building work has been carried out at a Grade II Listed Building.

“Our enforcement team is investigating the claim.”

Work on listed buildings is restricted to protect the historic significance of the building. Any change affecting the fabric of the building is illegal unless approved by the local authority, excluding routine repair work and maintenance. Cement is not allowed and mortar must match that used in the original build, and builders are forbidden from knocking off historic lime plaster.

Herts Advertiser: The back of the Duchess of Marlborough's almshousesThe back of the Duchess of Marlborough's almshouses (Image: Archant)

There are six almshouses in St Albans, the Duchess of Marlborough’s the biggest, and they were built to look after the poor, needy and elderly in the 18th century. In 2016, the almshouses were deemed to be in desperate need of refurbishment. Many changes were made in Victorian times, with a 1700s latrine replaced with a toilet block, however now trustees have to be mindful of restrictions due to the building’s listed status.

The almshouses have 36 small residential units to house people who are over 60 and have limited means.