The Last Samuri heads the final field of 40 runners in Saturday's Randox Health Grand National at Aintree. Sportsmail's Sam Turner analyses. PUNTERS are placing bets on their favourite horses ahead of the Grand National runners: Full list of horses and latest betting odds. Runners, riders, trainers and form - all the key details you need to know for Saturday's big race at Aintree. (Racecard number, horse, trainer.