A building on the estate where Princess Diana lived as a child has been targeted in an apparent arson attack.

The late royal’s brother Charles Earl Spencer has confirmed a farmhouse at the family’s Althorp House estate in Northamptonshire was set alight this week.

“Stunned to learn that one of Althorp House’s farmhouses – fortunately, unoccupied at the time – was apparently burnt down by vandals last night,” Earl Spencer wrote on social media on Wednesday (British time).

“Sincere thanks to Northamptonshire Fire and Rescue for trying to save it.”

On X, Spencer added that it was “so very sad that anyone would think this a fun thing to do”.

The fire service said later the blaze was on the Althorp estate in Mill Lane, Kingsthorpe, Northampton, rather than at Althorp House.

“Crews arrived to find an unoccupied two-story property fully on fire,” it wrote on Facebook.

“At the height of the fire, four crews from across the service wearing breathing apparatus used hose-reel jets to contain the blaze and prevent it from spreading further.

“One crew remained on the scene into this afternoon with a water bowser to continue dampening down any remaining hotspots.”

Long-standing gamekeeper Adey Greeno revealed more details about the fallout of the apparent attack.

“The farmhouse that we lost to a deliberate act of vandalism last night has now had to be razed to the ground for safety reasons,” he wrote on X.

“So sad. The world we live in.”

The stately home and its 5300-hectare estate has been the Spencer family’s seat since the 16th century. It was the childhood home of Diana and the earl, as well as their siblings Lady Jane Fellows, 68, and Lady Sarah McCorquodale, 70.

Diana lived there until she married the then Prince Charles in 1981 and became Princess of Wales.

She died aged 36 in a Paris car crash in August 1997, just a year after her divorce from the Prince of Wales was finalised. She is buried on a private island at the centre of Althorp estate’s Oval Lake.

Spencer still lives at Althorp. A year after Diana’s death, he opened up on the family’s unusual choice of a burial site for the princess.

“We all agreed that, with its beauty and tranquility, this was the place for Diana to be,” he wrote in his 1998 book Althorp.

-with AAP