Since finishing third to The New One in the 2013 Neptune Hurdle, Pont Alexandre had been off the track for two years but had managed three races this season and was well fancied for the four-mile National Hunt Chase.

He still seemed to be travelling well within himself when he was pulled up quickly before the 20th fence.

Mullins said: "It is a sad loss for the owner on what has been a great day. We never got to see the true extent of what he could do.

"He was a lovely big, old fashioned chaser and the type that had a laid-back personality. I thought I had him back this season and he will be sorely missed at the yard."

The Govaness was in the process of running an excellent race in the OLBG Mares' Hurdle for Dr Richard Newland, looking sure to be placed when she suffered a fatal fall at the last flight.

Jonjo O'Neill's Rezorbi was having just his second run for new connections in the Close Brothers Novices' Handicap Chase since joining from France when he fell two out and was humanely destroyed.

Jenny Hall, chief veterinary officer for the British Horseracing Authority, said: "We are sad to hear of the fatal injuries received today by The Govaness, Pont Alexandre and Rezorbi. Our thoughts are with the owners, trainers and all the staff who have cared for these horses.

"The BHA works closely with Cheltenham, and indeed all British racecourses, to ensure that the highest possible standards of welfare are in place at all fixtures. Each of the horses injured today were attended to promptly and received a high standard of professional veterinary care from the team at Cheltenham Racecourse.

"We record and monitor all injuries and fatalities that occur on the racecourse to provide a benchmark from which the industry continually strives to reduce injury rates. Over the last 20 years, the equine fatality rate has fallen by a third - and in 2015 was the lowest on record, falling to just 0.18 per cent of runners."

One animal rights group criticised Channel 4's coverage of the injured horses.

Animal Aid's Dene Strensall said: "It was particularly sickening that Channel 4 conspicuously failed to mention, as they finished broadcasting, that at least one serious injury had happened. Any self-respecting human being should condemn the use of animals in this way."

In response, a Channel 4 spokesperson underlined the nature of the injuries to The Govaness were not confirmed until its afternoon show was off air, while the other two races were not covered live, saying: "We extend our sympathies to all connections.

"We weren't given confirmation until we were off air and it is not our protocol to speculate.

"The other two incidents happened off air and we again extend our condolences to connections.

"Our highlights programme has taken into account the incidents of the day with care and consideration."