John Smith's Grand National, Aintree, Saturday, 1615 BST
BBC One/BBC HD/BBC Radio 5 live/online, with other races also across the BBC 8-10 April. Highlights: 0030, BBC Two
Sam Twiston-Davies rode a winner at the Cheltenham Festival
Sam Twiston-Davies is hoping for three more withdrawals in the Grand National to land a dream ride on Hello Bud for trainer father Nigel at Aintree.
Nigel Twiston-Davies trained Imperial Commander to victory in the Gold Cup a fortnight ago, and saddled two more Cheltenham winners that day.
One of those, Baby Run, was ridden by amateur jockey Sam, who is only 17.
BBC Sport has learned he can ride at Aintree even though he is one short of the 15 wins required to qualify.
A spokesman for the British Horseracing Authority said: "We've just had an email in from the Licensing Department confirming that the Licensing Committee has granted Sam Twiston-Davies' application to ride in the Grand National."
The famous race was last won by a 17-year-old in 1938, when Bruce Hobbs finished first on Battleship.
Nigel Twiston-Davies said of his son's ride on Hello Bud: "Sam's ridden him in his last three races. Nothing jumps as well as he does so it could be very exciting."
The Gloucestershire trainer is hoping to have six runners in the four-and-a-half mile marathon as he seeks to add to his past successes on Earth Summit (1998) and Bindaree (2002).
Stable jockey Paddy Brennan will ride Irish Raptor, a 40-1 shot, in the big race on 10 April in a bid to follow up his Gold Cup triumph.
Other firm bookings are Brian Hughes for Beat The Boys, David England on Ballyfitz and Tom Molloy for Ollie Magern.
Although that quartet are already guaranteed a place in the maximum 40-strong field, Hello Bud needs horses above him in the handicap to come out.
But with Twiston-Davies ruling out Razor Royale, and Irish trainer Tom Mullins confirming that Chelsea Harbour will miss the rest of the season,
only three more need to be withdrawn before 8 April
for Twiston-Davies junior to get his first ride in the Aintree spectacular.
Twiston-Davies senior said of his other entries: "Irish Raptor hasn't been quite right. He's had lung problems but he's come back now as good as he's been for a very long time.
"He does prefer the better ground. He's won round there and he's been second round there. He is my idea of a likely winner.
"Beat The Boys disappointed at Cheltenham but he too wasn't quite right. He's had a course of antibiotics and has come back really good.
"Ballyfitz is in great nick. They just went too quick for him at Cheltenham. He has made the odd mistake but, over a long distance, he can jump them in his own time.
"Ollie Magern is coming down in the weights, which has now given him a reasonable chance. He fell at the second fence last year, which was very uncharacteristic as he rarely makes a mistake at all.
"Knowhere made an uncharacteristic mistake at Cheltenham. He stood off the fence a mile away and couldn't get there.
"Go back two years and he was going really well two fences after Becher's, when he unfortunately unseated Joe Tizzard as he was getting into the race."