There are concerns that inadequate security fencing around a prestigious grade II-listed mansion in Brent has allowed arsonists to gain entry to the site and set the historic building ablaze.

Late on Sunday night, firefighters were called to a blaze at Dollis Hill House, which dates back to the 19th century, the Harrow Observer reports.

The police confirmed they are treating the incident as suspicious and Gill Close, a spokesperson for the Dollis Hill House Trust, said there were problems with the security fencing at the site.

"I am very concerned that despite assurances by Brent Council that adequate expenditure is budgeted for security, it is very easy for intruders to enter the site through the inadequate fencing surrounding the building," she told the newspaper.

"This might lead to a serious accident or injury any day soon."

The mansion, which has been derelict for a number of years, is scheduled for demolition. Eric Pickles, the secretary of state, is set to decide its fate within weeks.

Dollis Hill's famous guests have included author Mark Twain and former British prime minister William Gladstone.ADNFCR-3337-ID-800423796-ADNFCR