Stable hand Conor Murphy placed the bet as an accumulator on five of his boss’s horses before Christmas.

Last night, the final horse – 7-2 favourite Riverside Theatre – came good at the Cheltham Festival, allowing Murphy to trouser his windfall from online bookmakers

Murphy’s win circulated after BBC presenter Clare Balding revealed the details on Twitter.

She wrote: “he lad who looks after Finian’s Rainbow had a 5-timer on Nicky Henderson winners and has won £1m! Says he’ll be at work tomorrow.”

However, the 31-year-old horse-lover said the money would not change him.

Murphy tod his friends that he would be “straight back to work as usual” this morning.

The Irishman’s employer, horse trainer Nicky Henderson, said he  “couldn’t be happier for Conor.”

He added, “I’ve just heard about it – it’s absolutely wonderful.

“He’s such a lovely lad, one of the nicest you could ever meet. He’s my top guy and I’m absolutely thrilled for him

“He’s got amazing foresight betting on the horses before Christmas. I wish I’d known about it – I wouldn’t have minded making a million quid.”

Murphy backed the horses Simonsig, Bob’s Worth, Finian’s Rainbow and Sprinter Sacre.

The win of fifth horse, Riverside Theatre, completed his million-pound victory.

Henderson credited Murphy with his part in the success of Finian’s Rainbow, another horse which won the Queen Mother Champion Chase yesterday.