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 Nation at Aintree tomorrow. Here is a full list of runners and riders. How One For Arthur won the Grand National which should be more than enough time to stick pins into a list of horses, travel down to your.