The art dealer, who was 16 years older than Diana, was also a close friend of Prince Charles.
Former reports allege that Diana use to sneak Hoare into Kensington Palace in the boot of her car, and security staff once found him half-naked and hiding behind a bay tree as he tried to sneak out after a fire alarm went off in the middle of the night.
Diana once admitted, in the infamous Panorama interview with Martin Bashir in 1995, that she had called Hoare several times after he ended their affair.
‘Over a period of six to nine months, a few times, but certainly not in an obsessive manner, no,’ she insisted.
Hoare was a father-of-three and married to French oil heiress Diane de Waldner.
This article originally appeared on New Idea