Mr Frisk, who smashed the course record when winning the 1990 Grand National, was put down after falling on a road on Thursday.
His owner Tracey Bailey was riding the 21-year-old at walking pace on a road near Lambourn when he lost his footing and went down, fracturing his off-hind.
'Mr Frisk meant everything to me. I am devastated,' Mrs Bailey, the ex-wife of the gelding`s former trainer Kim Bailey.
'The road was wet and slippery and he simply lost his footing and went down in an instant. It wasn`t long before a vet arrived. Unfortunately, there was nothing that could be done to save the horse.
'I fell in love with him when we bought him at Doncaster Sales for 15,500 guineas as a seven-year-old after he`d been point-to-pointing in the north. He`d been a major part of my life ever since.'
Mrs Bailey was given the horse by US owner Lois Duffey when Mr Frisk retired in 1992, two years after he clipped 14.1 seconds off the Grand National course record when as an 11-year-old he beat Durham Edition by three-quarters of a length at Aintree in the hands of amateur Marcus Armytage.
Three weeks later, Mr Frisk made history by becoming the first (and only) horse to complete the Grand National-Whitbread Gold Cup double when the fast-ground specialist took the Sandown prize by eight lengths from his old rival Durham Edition.
