A 91-year-old retired solicitor who bet £500 at 6-1 he would be dead by Tuesday was in hospital on Monday but confident he would end up losing the wager.
Arthur King Robinson placed the bet after learning that if he died by that date his estate would become liable for inheritance tax of £3,000.
That is the same amount the bookmaker would pay out on his fatal flutter.
William Hill said it would not normally take that kind of bet but admired Mr King Robinson's ingenuity.
Mr King Robinson said on Monday that if he lived through Tuesday that £3,000 inheritance tax sum would be freed and would go to his estate when he eventually died.
Mr King Robinson, who practised as a solicitor in Crediton, Devon, until he was 84, has been in hospital for 10 weeks after suffering a blackout.
He placed the bet in the summer.
In his single room at Crediton Hospital he said: "Everyone is saying I look very well, though I do not know when I will be going home.
"The risk is I have a stroke between now and tomorrow," he said, adding, and touching the wood of his bedside table, "nothing is likely to happen now."
Mr King Robinson - not a betting man apart from the Derby, Grand National and occasional point to points - said he would be happy to lose the bet with William Hill.
William Hill spokesman Rupert Adams said it was not the kind of bet they would normally take, but this was "one of those rare occasions."
"When Arthur contacted us and explained the circumstances surrounding his wager, we were so impressed at his ingenuity in solving his taxing problem that we decided to lay him the bet - after all, if he wins, its his funeral."
His 85-year-old wife Cynthia said at their home in Crediton: "I do not know anything about it, I was far too busy doing other things. He just said he had done it."