He and Peterbilt headed home a 25-strong class, with fellow Kiwis Peter Breakwell second on Lucas, Rachel Fields (nee York) sixth on Karl du Chateau and Duncan McFarlane seventh on Mr Whoppy. Thomas rounded out the top 12 at the Capital City Classic in Sacramento, placing ninth on Vivaldi and 11th on Carino.

The historic third leg win earned him an extra $US70,000 in bonuses, and an ecstatic Thomas didn't even know what he had also amassed in prize money – probably around another $US80,000 for the three grand prix wins.

The 32-year-old is hopeful his efforts have caught the eye of New Zealand selectors, who are in the throes of naming a team to compete at the World Equestrian Games in Kentucky in September.

“This win is for my parents (Butch and Lou Thomas),” said Thomas. “I couldn't have better backers than them – they've put me on brilliant horses and in a spot to win.”

Which he has done very consistently in recent months.Thomas was last of eight to go in the jump-off today. 

Ahead of him Breakwell had set the pace that none had been able to match. However, Thomas and Peterbilt – who is a half brother to Katie McVean's (Mystery Creek) Dunstan Delphi, the current New Zealand Showjumper of the Year – not only went clear, but came home with two seconds to spare.

Thomas has won the rider bonus twice before, stopped in his clean sweep of the three grand prix last year by fellow Kiwi Anna Trent (Hawke's Bay).“

My horse has just been outstanding,” Thomas said of his 10-year-old mount. “He's been fantastic all year. Winning the Triple Crown is right up there for me – I feel finally I have really grown in my riding.”

Next weekend they'll start at the first of the Spruce Meadows tournaments, and he's hopeful he'll be at Kentucky in September.

“That's the goal. Hopefully all will stay as it is and I will keep riding properly and stay out of his way. He's a fighter this horse – just incredible.”

The Thomas' bred Peterbilt and Thomas has competed on both the dam and the sire with success.

“I hope I can keep it going, keep on wearing the New Zealand flag proudly and keep putting up good results.”It is the first time in the five years the Triple Crown has been running that one rider has won all three grand prix legs.