Nicky Henderson believes it will be "a nail in the National Hunt coffin" if Kempton is closed for housing redevelopment.
Henderson has saddled 58 jumps winners at the Middlesex circuit in the last five years, more than at any other jumps venue in Britain.
Perhaps even more tellingly, the 200 National Hunt runners Henderson has sent to the track during that period eclipses every other track apart from Cheltenham.
Long Run twice landed the jewel in Kempton's crown, the King George VI Chase in 2010 and 2012, while o ther Henderson big guns to have graced the Kempton winner's enclosure include Remittance Man, Simonsig, Sprinter Sacre and Altior.
Henderson told Press Association Sport: "It's a lot to digest, obviously. It's a massive subject and a massive deal.
"But I'm afraid, when it comes down to it, Kempton is a track National Hunt racing cannot afford to lose.
"We fought this battle once before and we won.
"They were talking about having the all-weather track and then Flat racing on the turf and doing away with the National Hunt.
"Thankfully we saw that little skirmish off and I think it's worked very well, with the all-weather and the jumps track side by side.
"It will be a very sad day if we lose it and I fear it will be a nail in the National Hunt coffin."
Owners Jockey Club Racecourses sent shockwaves across the sport on Tuesday when it announced Kempton could close by "2021 at the earliest" as part of a 10-year plan to invest at least £500million into British racing.
Should the proposed redevelopment go ahead, it has been requested by the Jockey Club that the King George and a clutch of other big Kempton races are moved to nearby Sandown.
"Kempton is unique, predominantly because of the ground," said Henderson.
"I had two or three horses that are due to run at Kempton this weekend that couldn't have run at Sandown last weekend, purely because of the ground.
"I know the two tracks are only five miles apart, but they are completely different and you need that variety.
"If you have a good-ground horse you go to Kempton, if you have a horse that wants softer ground and a stiff track you go to Sandown. It's simple.
"We have three metropolitan tracks - Kempton, Sandown and Ascot - and from my point of view, Kempton is the number one, and the ground is crux of it.
"The King George isn't the same race at Sandown and running the Christmas Hurdle there is a waste of space.
"If you want to run over a stiff two miles in soft ground, there are plenty of races for that.
"Sandown can't take that amount of racing. They (the Jockey Club) will tell you it can, but it can't, we all know that.
"Kempton is a very good racecourse, they provide the safest ground and we don't want to be without it."