【Old Gun slot】Grand National 2025: Breaking down the data with Pythia Sports

From sweepstake probabilities to the likelihood of a shock outsider finish, we dive into the data with Pythia Sports head of trading Jake Evans.

Evans has headed up trading for Pythia Sports managed services platform since it went live in 2020. He comes from a bookmaking background and has been on the trading side of B2C and B2B betting businesses for more than a decade. 

Q: The Grand National is known for its unpredictability, but just how many possible finishing permutations are there?

A: Given the field size of 34 runners, the possible first and second place combinations total 1,122. When you extend that to the first four home, the number of possible combinations explodes to 1,113,024. That’s part of what makes predicting the Grand National so tricky.

Q: Many people enter office sweepstakes for the Grand National. What are the chances of drawing the winning horse?

A: In a random sweepstake where each participant draws one horse, the probability of picking the winner is 2.94%. Once you’ve drawn your horse, your chance of winning depends on its actual odds. For example, if a bookmaker has priced Iroko at 8/1, the implied probability of winning is around 11%. However, factoring in the bookmaker’s margin (or over-round), the true probability drops slightly — likely closer to 9%.

Q: Predicting the first four finishers in order must be incredibly difficult. Just how unlikely is it?

A: If you’re making a completely random guess, the probability of selecting the first four horses home in exact order is just 0.00009% (or 1 in 1,113,024). Even if you had an exceptional strike rate of being correct 1 in 10 times when making race predictions (which would be impressive), your chance of getting the first four in order would still be just 0.01% — or 1 in 10,000.

Q: What about a real long shot? How unlikely is it that the four biggest outsiders take the top four spots?

A: Based on current betting markets (as of 1 April), four of the longest-priced entries include Twig, Duffle Coat, Fil Dor, and Broadway Boy. If they were to fill the first four places, the estimated probability would be an astonishingly low 0.000000013% — or roughly 1 in 75 million!

Q: Irish-trained horses have dominated in recent years. What’s the likelihood of an all-Irish top four?

A: At present, 29 of the 57 entries are trained in Ireland. More significantly, six of the top seven in the betting come from Irish yards. Based on current probabilities, the likelihood of an all-Irish-trained top four is around 15%.

Q: The Grand National is notorious for its demanding course. What are the chances of only Irish horses finishing the race?

A: Historically, the race has had a low completion rate. Over the last 25 Grand Nationals, an average of 39% of horses have finished, with 2001 seeing a record-low four finishers from 40 starters. However, safety modifications have increased completion rates, with 65.6% finishing last year.

Assuming a 60% completion rate this year and half the field being Irish-trained, the probability of only Irish horses finishing the race is roughly 1 in 20 million (or 0.000005%).

About Pythia Sports

Pythia Sports was established in 2014 with a focus on predictive sports modelling and data collection, primarily in racing. It works in partnership with data rights holders such as Arena Racing Company and Racecourse Media Group (RMG). It has recently worked with the latter to launch an in-play betting feed, for which Pythia provides the pricing to clients including William Hill, Ladbrokes, Coral and William Hill.