Racing punter stands to win more than £500,000 from a £5 bet if Envoi Allen wins at Cheltenham.

A horse racing punter incredibly stands to win more than £500,000 if Envoi Allen delivers the goods in the Marsh Novices Chase at Cheltenham Festival on Thursday. 

Paul Dean, who goes by the Twitter name @istabraq_king, took to social media on Wednesday to share the remarkable bet after Bob Olinger clinched victory in the Ballymore Novices Hurdle at Cheltenham.

After Rachael Blackmore struck again with Bob Olinger, it meant Paul now just needs Envoi Allen, who is favourite at 4/9 with Betfair, to win Thursday’s opening race for him to walk away with £511,225.

Betfair have confirmed that if he opted to cash out, the racing fan would still win an astonishing £275,000 from the £5 bet he made last June.  

When revealing the eye-watering accumulator, Paul wrote on Twitter on Wednesday: ‘Praying for Envoi tomorrow’, alongside a praying emoji. 

Sportsmail has approached Paul for comment. 

In the betting slip, the racing punter’s first horse came in last June at Royal Ascot as Golden Horde won the Commonwealth Cup at 12/1.

A day later, Hello Youmzain at 10/1 reigned supreme in the Diamond Jubilee Stakes at Ascot.

And fast forward to this year’s Cheltenham Festival, he won with Shishkin at 4/1 in the Arkle Chase on the opening day on Tuesday before Bob Olinger (25/1) triumphed on Wednesday.

Now with just one more race on the line, his nerves must be shredded as he has a huge decision to make – whether to cash out for £275,000 or gamble and hold out for over half a million. 

Racing fans flocked to social media to wish their best to the punter, and one user even commented: ‘This chap isn’t sleeping a wink tonight! Good luck.’

Paul amusingly replied: ‘Will try my best’, alongside a picture of plenty of alcohol – presumably to calm the nerves.

He then posted a picture of himself holding a champagne bottle called ‘Bolinger’ – with the caption: ‘Celebrating the Bob Olinger victory while deciding what to do.’

Betfair spokesman, Barry Orr commented on Wednesday: ‘The customer is sitting on over half a million pound payout for just a £5 bet and told me he wont be able to sleep tonight. I’d say that’s a massive understatement’

‘He could take the cash out offer of £275,000 and sit back safe in the knowledge that regardless of what happens in the race he is £275,000 better off, or he can reject the offer and hope that Envoi Allen beats his 7 opponents and also safely negotiate the 16 fences to land his incredible bet.’

‘Envoi Allen is 4/9 favourite so he may well stick and let the bet run.’  

Paul will find out his fate, unless he cashes out, at 1:20pm on Thursday as the Marsh Novices Chase kicks off the drama on day three. 

Envoi Allen, who is already a dual winner at the Festival. remains unbeaten in his career and his season on the track has been smooth – with three victories in Ireland under his belt.