As the world's most famous steeplechase and with 40 runners going to post every year, finding the Grand National winner can be tough even for seasoned horse racing punters. But what are the key trials?
There are plenty and those races listed below don't include the official Grand National Trial at other Merseyside venue Haydock in February, because horses that go in that and then on to Aintree have a notoriously poor record. We've split the races into two categories; traditional British trials and Cheltenham Festival races that can have a bearing on the Grand National.
A logical place to start with Grand National trials is a race over the same course but around a mile or so shorter. The Becher Chase, a Grade 3 handicap run in December, can give National hopefuls much-needed experience of the spruce-covered fences like the Canal Turn and The Chair.
One For Arthur, who won the big one in 2017, was a three-length fifth in the Becher before going on to land the similar grade Classic Chase over an extended three-and-a-half miles at Warwick. Walk In The Mill triumphed in the Becher this season off a light weight and is 33/1 over on Paddy Power in the Grand National.
Other obvious staying handicap chases that can serve as trials for Aintree are the Welsh Grand National at Chepstow run over Christmas and the previous season's Scottish Grand National at Ayr. The latter is one of the few other four-mile races during the British jumps calendar.
Another is the Eider Chase at Newcastle, which is run in February. Comply Or Die won both that and the Aintree marathon back in 2008. The Midlands Grand National at Uttoxeter in March is the closest UK trial in proximity to the race, and Milansbar, a Classic Chase winner as reported here, who finished second in that, was the best-placed British runner in the 2018 Grand National in fifth.
There are many stayers' events throughout the four-day Cheltenham Festival in March, which can be as long as 30 days before the Grand National takes place. Novices deemed to have a big future in endurance tests often run in the National Hunt Chase for amateur riders.
This four-mile contest was notably used by Cause Of Causes - second at Aintree in 2017 - and last year's Grand National hero Tiger Roll to launch their careers as stayers. Both went on to win the following season's Cross Country Chase over three-and-three-quarter miles when coming back to the Festival in open company. A similar plan - as explained here - is in place for Tiger Roll this year and he's 25/1 to repeat his Aintree heroics.
Cross Country races are popular Grand National trials because horses going in those have to jump a variety of obstacles at different heights. The Aintree course does have some regulation fences, but the Cheltenham Cross Country event seems to stand those taking to it in particularly good stead for the National.
Some horses that go in the Cheltenham Gold Cup itself over three-and-a-quarter miles simply want further. If lacking the class to win the blue riband event of British steeplechasing, they can then go on to do well in the Grand National. Many Clouds and Anibale Fly are notable recent examples, with the latter placing at both Cheltenham and Aintree.