Red Rum. Foinavon. Mon Mome at 100-1. The Grand National has produced more jaw-dropping results than almost any sporting event in history, and it does so every April at Aintree over four and a quarter miles of fences with names like Becher's Brook and The Chair. It is chaotic, emotional, and statistically brutal to price correctly.
Why the National Is Particularly Hard to Price
Forty runners means the favourite wins far less often than in a conventional 10-runner chase. Falls, unseated riders, and interference mean the race plays out like a survival game first, a horse race second. Bookmakers know this — which is why their each-way terms (typically 5 places at 1/4 odds) look generous but are carefully calibrated to extract maximum margin.
An each-way bet is two bets — a win bet and a place bet. The place bet on a 40-runner race is priced at 1/4 odds for 5 places. Work out the implied probability. Then compare to Boromarket's YES/NO on a top-5 finish. The difference is usually illuminating.
Longshot Winners and Market Efficiency
- →Mon Mome (2009): 100-1 winner, completely ignored by the market
- →Foinavon (1967): 100-1 winner following mass pile-up at 23rd fence
- →Tiger Roll (2018, 2019): back-to-back wins, priced fairly in advance
- →Corach Rambler (2023): well-fancied winner, market had it right
The National is the race where prediction markets are at their most honest. There is no illusion of certainty. Every runner genuinely could win. Trade accordingly.