JT McNamara was airlifted to hospital in an induced coma after being injured in a fall at the Cheltenham Festival.
The renowned amateur rider was partnering Galaxy Rock for trainer Jonjo O'Neill in the Fulke Walwyn Kim Muir Challenge Cup when the pair crashed out at the first fence.
Medical staff were quickly on hand to treat McNamara and it was decided to transfer him to Frenchay Hospital in Bristol for further treatment without delay.
Course spokesman Andy Clifton said: "JT McNamara is being transferred to Frenchay Hospital in Bristol via air ambulance and continues to undergo assessment."
The rider was reported to be conscious following the fall, but McNamara's uncle, the trainer Andrew McNamara, said: "I've been told that JT is in an induced coma at the moment."