Sixty riders from 20 nations are taking part in three days of five-star competition at the Horse Guards Parade Ground in the heart of the capital.
It will be the final opportunity to see many of the world’s leading riders in action before the Alltech FEI World Equestrian Games in France later this month.
Scott will be joined in London by his world championship team-mates Ben Maher and Michael Whitaker. Other leading British names include Guy Williams, Robert Whitaker, William Funnell and Peter Charles.
They will compete against some of the best riders in the world such as Ludger Beerbaum, Eric Lamaze, Beezie Madden, Steve Guerdat, Edwina Tops-Alexander and current GCT series leader Rolf-Goran Bengtsson.
The winner of last year’s GCT grand prix in London Ben Maher said: “Everyone on the Tour is capable of winning the big grand prix in London. But at the moment Scott Brash is one of my biggest rivals and we’ll be doing our best to get a home win.”
London Mayor Boris Johnson also welcomed the return of the series following its inaugural show at the Queen Elizabeth Olympic Park in 2013.
“London is the home of world-class sport and I would actively encourage more sports to come and experience everything that makes it the best big city in the world,” he said
The action will be shown on BBC2 on Friday (3pm-5pm) and Saturday (5.15pm-7pm).