Described as "an eccentric recluse", Dale was found bludgeoned to death in his countryside mansion in Heath, Herefordshire, England.
The only suspect, Dale's former wife Baroness Susan de Stempel, was cleared of his murder due to insufficient physical evidence.
Though the investigation into Dale's murder did not finish with any convictions, there were successful charges of fraud against de Stempel, two of their children, and her new husband.
Ignoring the scepticism of archaeologists, he believed that Hopton Heath was an integral part of the legend and that the Holy Grail was buried in the area.
[1] Susan found life after her first marriage to be very difficult and had to rely on handouts from her family, finding a home in Docklow, near Leominster.
De Stempel was from a wealthy Russian family, the holders of an ancient Latvian title, and their marriage was part-funded by the sale of her aunt's jewellery.
Dale was found dead in the kitchen on 13 September 1987, food still cooking in the oven, by Giselle Wall, his editorial assistant.
Dale's headstone in the churchyard of St Edward's, Hopton Castle, is inscribed with "11/12 September 1987" as the date of death.
Investigations into the whereabouts of Margaret's thirty gold bars, valued at £12 million, proved fruitless despite a dig in the grounds of Heath House.
It is also the basis for the true crime book Blood Money: The Story Of The Baroness de Stempel Scandal by Kate Wharton.
[6] The case also serves as the inspiration for The Jesse Tree by Linda Hurcombe,[7] a 2018 novel in which the murder, the trial and the gold bars are woven into the fictional story of a young Romany Gypsy and her friend.