Brash and world number two - his fellow British London 2012 gold medallist Ben Maher - will be among a high-class field in Saturday's Longines FEI World Cup class at the London International Horse Show.
Maher is among the list of previous Olympia World Cup winners, and his battle with 28-year-old Brash will underline the unprecedented feelgood factor currently engulfing British showjumping.
With Britain holding Olympic and European team titles simultaneously - a feat only previously achieved by Germany - Brash and Maher also winning European individual medals this year and Brash being crowned overall Global Champions Tour winner, both riders are at the peak of their powers.
Brash, who only made his senior Great Britain debut little more than three years ago, has enjoyed sustained success on his top horses Hello Sanctos and Ursula, both owned by his established backers Lady Kirkham and Lord and Lady Harris.
Sanctos, second in the Geneva grand prix behind reigning Olympic champion Steve Guerdat last weekend, is rested this time round, with Brash making his London challenge on Ursula.
"I didn't think I could get to number one as quickly as I have," Peebles-based Brash said.
"It was always my main aim after the Olympics, but I didn't think it would happen a year later. I thought it would take four or five years.
"Everything has to go right, but I am just very fortunate to have the owners behind me that I do, the horses that I have and the people behind me. That's what makes it the success it is.
"Every sportsman and sportswoman, I think their ultimate goal is to try and become number one in their sport and be the best they can be.
"To achieve that goal means a lot. All the hard work put in by all my team throughout the years has paid off, and I am very grateful for everyone's help for helping me get where I am today."
Brash, famously described by Great Britain team boss Rob Hoekstra as having "ice in his veins" when it comes to jumping pressure rounds, will be an integral part of Britain's bid for world championship glory in France next summer.
If the team triumphs in Normandy, it would complete a title clean sweep of world, Olympic and European crowns.
"Once you get the horses that can go and win, for sure it makes life easier and helps you breathe easier.
The owners of the horses are just amazing, and I am in a very good place just now," Brash added.
"I think everyone is looking for a half step-up in life, but you don't get it sitting still.
"You have got to go out, prove yourself and take your chances, and I am just very grateful that they noticed me and what I was doing and chose me to put the backing into.
"Having myself and Ben at the top of the world rankings is great for British showjumping.
"We are very good friends. He is very professional in what he does, and I think if there is any rivalry at all there between us it is all very good and friendly. We spur one another on."