Conor Murphy placed a bet, believed to be only £50, on the horses late last year when the odds were good, and saw all five come in as winners.
The Cork-born 31-year-old admitted he was still in a state of shock after landing the bet but still managed to turn up for work on Friday morning.
“I still cannot believe it, even this morning it is still sinking in. I haven’t even thought about the money yet. It was just pure luck,” he told Newbury Today.
“I put the bet on just before Christmas in December, I just picked the five best horses and hoped for a lot of luck, I didn’t think much about it."
Murphy's winning spree began with Sprinter Sacre's victory in Tuesday's Arkle and was followed on Wednesday by victories from Simonsig in the Neptune Investment Novices' Hurdle, Bobs Worth in the RSA Chase and Finian's Rainbow in the Queen Mother Champion Chase.
He then sealed his bet – which he placed online with Bet 365 – when Riverside Theatre won the Ryanair Chase on Thursday.
"From the moment it set off it never looked like winning, he made loads of mistakes and looked miles off," Murphy said of the final leg of his bet.
"I wasn't really thinking about the bet when they all started coming in; you try so hard to get even one winner here, the day just draws you in."
Trainer Henderson, who has had a total of six winners at the Festival in all, said he was delighted for Murphy.
"Everybody here is absolutely thrilled for him," he said. "It was just an amazing piece of foresight. Just the chances of all five getting to Cheltenham and all of them running in the right races, that would be long odds, particularly as with Simonsig - we didn't even know what race he would be running in until the other week. The chances of them getting there must have been at least 100-1.
"He's the most lovely man though, a fantastic guy and very quiet. He rides out Finian's Rainbow every day of the week and he would probably know more than anyone else in the world about that horse."
The only Henderson-trained winner Murphy did not have in his accumulator was Une Artiste, who triumphed in Wednesday's Fred Winter at 40-1.
"He's backed five out of our six winners and he couldn't even have backed the other one as she wasn't in the yard then, she was still in France," explained Henderson.