Oxfordshire owner-breeder Roger Nicholls will be on tenterhooks when his pride and joy Ollie Magern tackles the John Smith’s Grand National at Aintree on Saturday.

The 66-year-old self-employed building contractor, from Milcombe, near Banbury, had hoped to see the gelding run in the world’s most famous steeplechase 12 months ago only for his charge to go lame just days before the race.

But now it’s all systems go for the 11-year-old from the Gloucestershire stables of trainer Nigel Twiston-Davies, who has already enjoyed National glory with Earth Summit and Bindaree.

There has been one late hiccup this time though with Ollie Magern’s intended jockey, Tom Molloy, being ruled out as he hasn’t ridden enough winners over fences to take part in the National.

Instead Sam Waley-Cohen, from Edge Hill, near Banbury, a three-times winner over the big fences with a brace of successes on Katarino in the Fox Hunters’ Chase and a triumph aboard Liberthine in the Topham Chase, comes in for the ride.

Nicholls said: “I am gutted for Tom. I had promised him the ride, but he has only won 13 races over fences and to qualify for the National you have got to have ridden 15.

“Sam is riding him now. He took him up the gallops and he gave him a lovely feel.”

Nicholls bred Ollie Magern out of his mare Outfield, a daughter of the dual Champion Hurdle winner Monksfield, after sending her to another Champion Hurdle hero,Alderbrook.

“My young groom, Fiona Quincey, named him Ollie when he was born and Magern came from a late uncle and aunt of mine called Maggie and Ernie,” Nicholls recalled.

And the bay gelding has proved a real star, winning the Feltham Novices’ Chase at Kempton and two Charlie Hall Chases at Wetherby.

Now Ollie Magern faces his biggest test.

“Nigel wanted him to run in it when he was a novice, but I wouldn’t let him because he has been a brilliant horse to me, so for Saturday I want him to come out of it safe and well – that is the main thing,” added Nicholls.

“I think like last year as a ten-year-old and now as an 11-year-old is the time to go for it. He has done me proud. The ground will suit, the flat track will suit and he will jump the fences for fun.”

Ollie Magern has been dismissed by the bookmakers, who make him a 100-1 outsider.

But his owner believes he has a much better chance than those odds suggest.

“Hopefully he can get out in front over the first two or three fences because that is where the accidents happen, and then get settled,” said Nicholls, who also owns land for arable farming and coarse fishing.

“The horse doesn’t know what price he is. I think he can be in the first eight as long as he has a clear round, if not nearer. He is up there in the weights, but they don’t put weight on donkeys. He has got a good heart and engine, and always does his best.”