Santini lived up to his billing with an impressive debut over fences in the Ladbrokes John Francome Novices' Chase at Newbury.
Having signed off last season with a Grade One victory at Aintree, the imposing six-year-old made a seamless transition to chasing in the extended two-mile-seven-furlong contest.
Although making one mistake mid-race, the 11-8 favourite made his class count when wearing down the prominently-ridden Rocky's Treasure after the last in the Grade Two prize, before clearing away to score by four lengths under Nico de Boinville.
He was cut to 3-1 for the RSA Chase at the Cheltenham Festival in March by both Unibet, Paddy Power and Betfair, while Coral went 9-2 for the same race.
Henderson said: "You would have to be very pleased about it. I was nervous about the ground. He is a beautiful horse, but he is big and he is gross. He is quite laid-back about it at home.
"We got on the grass on Thursday to school and that was the first day he has woken up, but he is like that. I couldn't believe he was straight enough, to be honest. He is so lazy about it all. I thought it was a great performance.
"Nico gave him a lovely ride, as he let him find his feet, and although he made a couple of little mistakes, he let him think about it.
"He jumped a couple a little bit big, but he was just learning and he will learn a lot for today and he will come on any amount."
Looking to future plans, Henderson pointed towards Kempton Park on Boxing Day.
He said: "I suppose he will have to go to Kempton (Kauto Star Novices' Chase), as there are so few you can run him in."