Guery won in 39.57 seconds aboard Quel Homme de Hus, which booked him a place at the Super Grand Prix in Prague in November. 

It also earned him €102,630 (£88,796/$116,172) in prize money. 

Second was Egypt's Abdel Saïd in 40.53, while Harrie Smolders of the Netherlands finished third in 40.74.

“I have only been riding this horse for two months, so the combination is really new," Guery said. 

"The horse comes from my best friend. 

"He gave it to me as he knew it was a special horse and he deserved to go to five-star shows. 

"I didn’t expect to win today and I’ve never had a feeling like this about a horse. 

"Mexico City is my favourite LGCT – it’s an amazing show.

"I like the big arena and as my first LGCT this year, to start with a victory is amazing.”

The third leg of the LGCT takes place on Miami Beach from April 18 to 20.