Scaffolding has been erected around the soon-to-be demolished spa pool building that was built without permission at the home of Captain Sir Tom Moore's daughter.
A flatbed truck arrived at the home in the Bedfordshire village of Marston Moretaine on Tuesday morning and drove into the grounds through a gate off a residential street at the rear of the plot.
Scaffolders in orange hi-vis jackets could be seen moving metal poles around the unauthorised building as work began.
Hannah Ingram-Moore and her husband Colin lost an appeal against an order to remove the spa pool block, which they named the Captain Tom Foundation Building, in the grounds of their property after a hearing in October 2023.
Inspector Diane Fleming ruled in November that the spa block must be demolished within three months, meaning it would have to be brought down by 7 February.
Central Bedfordshire Council has said it will be "reviewing the on-site position" on 8 February.
The deadline for the appeal decision to be challenged in the High Court passed without a claim being issued.
Planning permission had been granted for an L-shaped building in the grounds of the family home, but the planning authority refused a subsequent retrospective application in 2022 for a larger C-shaped building containing a spa pool.
Central Bedfordshire Council issued an enforcement notice in July 2023 requiring the demolition of the "unauthorised building" and the Planning Inspectorate dismissed an appeal against this.
During a hearing in October, chartered surveyor James Paynter, for the appellants, said the spa pool had "the opportunity to offer rehabilitation sessions for elderly people in the area".
But Ms Fleming's written decision concluded the "scale and massing" of the building had resulted in harm to the Grade II-listed Old Rectory - the family's home.
The foundation is the subject of an investigation by the Charity Commission amid concerns about its management and independence from Sir Tom's family.
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The charity watchdog opened a case into the foundation shortly after the 100-year-old died in 2021, and launched its inquiry in June 2022.
Scott Stemp, representing Ms Ingram-Moore and her husband, said at the appeal hearing that the foundation "is to be closed down following an investigation by the Charity Commission".
Sir Tom raised £38.9m for the NHS, including gift aid, by walking 100 laps of his garden before his 100th birthday at the height of the first national COVID lockdown in April 2020.
He was knighted by the late Queen during a unique open-air ceremony at Windsor Castle in the summer of that year.
He died in February 2021.