Northamptonshire - "Sounded like someone flushing a gigantic bog," one of the Althorp House groundsmen said today as news of the disaster broke.
Witnesses described how the burial island 'went down the plug hole' as a downpour wiped out the Princess' last resting place.
The torrential deluge over Althorp Village completely devastated Diana's island grave in the middle of the Round Oval ornamental lake.
Within minutes of the storm breaking the burial sepulchre sank without trace 'somewhere beneath the Northants water table'.
And it could be weeks before attempts to pump out the flooding as structural engineers weigh up the damage.
"We think it's been swallowed up by an ancient mine shaft," the Queen's Surveyor of Disasters said, "one of many left to rot by the defunct Coal Board which abandoned the collieries back in 1968."
News of the sinking has left Earl Spencer absolutely gobsmacked ahead of the traditional, extremely lucrative public viewing season at the royal mausoleum.
The price of a ticket for a 30-second gawp has only gone up to fifty quid.