A reporter posed as a member of stable staff at Aintree and entered the box of last year's winner, Hedgehunter.

Peter Webbon, chief executive of the Horseracing Regulatory Authority, said: "This was not a spontaneous act.

"It was timed to coincide with the Fox Hunters' Chase when the security team might be less familiar with the stable staff entering and leaving."

After gaining entry to Hedgehunter's box, the undercover newspaper reporter posed for a photograph with the horse, which was taken by the driver of the horse's trainer, Willie Mullins.

There was never any risk to the horse Hedgehunter's trainer Willie Mullins

"We will be speaking to all of the staff concerned in more detail to see what lessons can be learned from this," added Webbon.

"At this stage I cannot say if we will be taking action against the newspaper involved."

Both Webbon and Mullins stressed that there was no risk to Hedgehunter during the breach, as the gelding was never left alone.

Mullins said: "I have spoken to the girl, Mia, who looks after Hedgehunter and she was with him the whole time.

"It is certainly not unusual to be asked for this sort of thing, we get requests regularly.

"I think that if someone is determined to get into the stabling area then they will do. They appear to have done a good job in gaining entry.

"I have spoken to Mia and there was never any risk to the horse."

Charles Barnett, managing director of Aintree Racecourse, said: "The responsibility of the stable yard on a race day lies with the Horseracing Regulatory Authority.

"There is a comprehensive CCTV system installed which enables the HRA security officers to monitor both the access to the yard and movement within it.