The fences at Aintree have this year been changed for safety reasons but Twiston-Davies, whose son Sam was on board the 11-year-old, is refusing to blame the fences.
He said: "He's gone out doing what he loved the most, he's jumped round those fences before and it's one of those things.
"It could happen anywhere, it could happen at home and it's not the fences - it could have happened at a park course.
"It's desperate, as he is one of Sam's favourite horses and he has been a great servant."
Twiston-Davies's best hope in today's Grand National, Imperial Commander, is looking to become the third horse to win both the Cheltenham Gold Cup and the National.