A burglary last year at the Grade-I-listed Wimpole Hall caused “extensive damage” and 12 “historic items” were stolen, the National Trust has said.

The front doors were broken in, “apparently with a sledgehammer”, the Trust has said, blaming “vandals”.

The incident occurred in November, and the National Trust, which owns the house-turned-museum, has now applied for planning permission to repair and reinforce the neoclassical mansion’s primary entrance.

First built in the 17th century, with a facade updated in the 18th century, Wimpole Hall is part of the Wimpole Estate and is known as the largest house in Cambridgeshire.

Cambridgeshire Constabulary confirmed it was called to reports of a burglary at the property in Arrington just after 6pm on Sunday, November 8.

A spokesperson said “officers attended and discovered an untidy search of the building had been conducted and items had been stolen”.

An investigation was launched but no arrests have been made, the police said.

The National Trust said “a number of busts, lamps and vases were stolen from Wimpole Hall and several more damaged”.

The conservation charity said it has “taken extra measures to ensure the security of the rest of the collection”.

Among the items reported stolen were a pair of 19th century Japanese Imari vases decorated with animals and birds, and a French ormolu four-light candelabra on a marble urn with rams’ heads.

As part of the National Trust’s planning application submitted to the Greater Cambridge Planning Service in March, a cultural heritage curator for the Trust, Dr Jane Eade, said “a failure to improve security of these doors leaves the collection vulnerable to repeat attack now the building has been entered using force at this access point”.

The application says: “Two staff flats are situated at first floor level, one each either side of the front door.

“The ease with which the vandals were able to hack the doors and gain entry to the Hall, despite the sounding of alarms, has made all resident staff nervous about their safety. Keeping our staff safe is of paramount importance to the National Trust.”

The principal front entrance to Wimpole comprises two sets of doors, one of which dates back to the 19th century, and both have been damaged, and now require “extensive conservation treatment”.

The in addition to the 12 items stolen, the application says three others were damaged in the break-in.

The application says the doors are being repaired, but is requesting the use of stronger materials to reinforce them. The additional measures proposed have successfully held back a repeated break-in attempt at another National Trust site in the past, the application says.

“Thankfully no loaned items in the entrance hall or beyond were affected,” the application says.

“Our lenders, as well as our insurers, are waiting to hear that appropriate additional safeguards have been put into place and that Wimpole’s status as an Accredited Museum is not at risk.

“The hanging of loaned paintings in this space, associated with the families of Wimpole’s ‘heyday’ in the eighteenth century, have been crucial for setting the scene of the sporting and antiquarian nature of the estate as one enters the house”.

Anyone with any information is urged to contact us via our web chat here: https://bit.ly/2D9KFKH or call 101, quoting crime reference 35/76045/20.