It's a level playing field for all of the runners – until the tapes go up

Two past winners and 38 wannabes line up, but some chances seem more obvious than others. Chris McGrath guides you over the obstacles and past the pitfalls

Hot Shots

Arbor Supreme

Hampered when unseating at halfway last year but lightly weighted, shaped well in his rehearsal, loves a test of stamina and drying conditions are in his favour. Odds 20-1

Becauseicouldntsee

Has long looked an ideal type and excelled against Majestic Concorde last time. Just a pity his preparations have been interrupted by minor surgery. Odds 25-1

Character Building

Tired into seventh last year only after making up loads of ground from rear, and has had better preparation now. Rider well qualified to be first woman to win National. Odds 25-1

The Midnight Club

Has the priceless assistance of Ruby Walsh and Ireland's top trainer. Still improving, won a strong trial and has been craving a proper test of stamina. Odds 10-1

What A Friend

Career best when fourth in the Cheltenham Gold Cup, a run that would require him to carry much more weight in future. Big chance in Sir Alex Ferguson's colours. Odds 12-1

Coming To The Elbow

Ballabriggs

From the stable that gave us Red Rum, his bold style has long looked ideal for Aintree. But how much petrol will remain in the tank for the long run-in? Odds 14-1

In Compliance

Once threatened to be top-class, and is kindly weighted. Lost apprentice rider last time but ran well over these fences last year and attractive odds if lasting home. Odds 66-1

Oscar Time

His dashing amateur rider has won the Cheltenham Gold Cup and he shaped well in his rehearsal, although did not quite last home in the Irish National last year. Odds 12-1

Skippers Brig

Looks dangerously weighted after beating Ballabriggs in their warm-up, and could improve again over this distance, but drying ground is a worry. Odds 33-1

State Of Play

Goes well here, and best fresh, so audaciously held back since finishing third last year. Unlikely to give the leaders such a start this time, and is fairly weighted. Odds 25-1

In Midfield

Backstage

Top jockey and trainer, and similar preparation to his stable's 2007 winner, Silver Birch, but requires a leap of faith in terms of both form and stamina. Odds 12-1

Bluesea Cracker

Wore down Oscar Time in the Irish National last year and has shaped well in her build-up, though it is uncertain how she will cope with faster ground. Odds 25-1

Don't Push It

Managed to exorcise Tony McCoy's Aintree curse last year, and has enjoyed a similar preparation, but must concede weight all round this time. Odds 10-1

Dooneys Gate

Represents Ireland's top stable and ran well over these fences last season, but stamina is uncertain and his amateur partner has won just one steeplechase. Odds 66-1

Golden Kite

Forget his warm-up over hurdles in bad ground and you could give this dour stayer a chance at big odds, with a good strike rate in these conditions. Odds 50-1

Killyglen

Signs of renewal for new stable and ran better than it appeared last time, burning up too much fuel in sharing a hot pace. Type to relish the distance. Odds 50-1

Majestic Concorde

Inexperience a concern after competing in just seven steeplechases, but impressed last time and top connections make the odds tempting. Odds 28-1

Niche Market

Won the Irish National for his previous trainer but Walsh turned him down after he showed little over an inadequate distance at Newbury last time. Odds 20-1

Silver By Nature

Scottish grey would have been given more weight after a runaway success in Haydock mud, but ability to match that on faster going unproven. Odds 14-1

Tidal Bay

Hopelessly unreliable, but has the talent if he has got out of bed the right side, and a very able rider, too. Might just down tools if it looks too much like hard work. Odds 33-1

Outsiders

Big Fella Thanks

Going well on home turn last year but ultimately beaten miles into fourth and his new trainer, who excels with stayers, must find new reserves from somewhere. Odds 16-1

Calgary Bay

Might take to this challenge, as he can jump and travel with gusto, but whether he will retain energy for the final slog is another question. Odds 33-1

Can't Buy Time

Failed to get round in the last two runnings, and has had a season of fits and starts, but fairly treated at the weights on his very best form. Odds 66-1

Comply Or Die

First in 2008, second in 2009, but faded badly last year and has shown little sign of life since; fairly weighted but surely vulnerable to younger legs. Odds 50-1

Hello Bud

Nearly as old as his jockey but again jumped brilliantly when winning over a shorter distance here in November. Stamina ran dry, however, when fifth last year. Odds 33-1

Quinz

Flamboyant youngster who would have more weight in future, but most of his form is on right-handed (clockwise) tracks and he remains very short of experience. Odds 16-1

Royal Rosa

Has had his moments round here, twice runner-up over these fences, but was taken off his feet when unseating his rider at halfway in this last year. Odds 80-1

The Tother One

Has hinted at better, given a test of stamina, but has increasingly looked too inaccurate over his fences, and too irresolute when the chips are down. Odds 66-1

Vic Venturi

Has won round here but lacked fluency before coming down last year, has plenty of weight to carry, and his stamina open to doubt, too. Odds 50-1

West End Rocker

Top connections, so worth forgiving his blip last time, but suspicion is that previous improvement in a lower grade was insufficient to get him involved here. Odds 33-1

Foinavon Fodder

Chief Dan George

Won at the Cheltenham Festival last year but already under pressure when early faller on his return there, hardly threatening an imminent return to form. Odds 40-1

Grand Slam Hero

Flourished last summer but made no show on his return from a break last time, and his jumping has looked too diffident to cope with a test like this. Odds 100-1

King Fontaine

Has not coped with a step up in class after reeling off four wins in lesser company, soon struggling to find a rhythm at Cheltenham last time. Odds 66-1

Ornais

Entitled to be rusty on both starts since a long absence, but his best form has come in small fields and this will be a very different kettle of fish. Odds 66-1

Or Noir De Somoza

Impossible to know what to expect from this French import, prolific over shorter distances, but odds are against him winning a National at the drop of a hat. Odds 50-1

Piraya

Lacks stamina and probably commitment, too. Tailed off at 100-1 last season and recent starts promise little better, after he took no interest at Cheltenham. Odds 150-1

Quolibet

Recent French import who offered precious little on British debut, sent off at 50-1 and failing to cut the mustard in undemanding company at Cheltenham. Odds 125-1

Santa's Son

Must make surreal improvement at 11, having spent his career making only a modest impact at shorter distances, finishing well beaten most recently at Cheltenham. Odds 200-1

Surface To Air

Ancient history records that he won three of his first four steeplechases but that was nearly three years ago, and finished tailed off last over hurdles on his comeback. Odds 66-1

That's Rhythm

Ready for a fresh start but only those with long memories will remember him cruising when falling in the Scottish National a couple of years ago. Odds 150-1

Our experts' predictions for today's National

Chris McGrath, Racing Correspondent

1. Arbor Supreme

2. Becauseicouldntsee

3. The Midnight Club

4. Character Building

Sue Montgomery, Racing Writer

1. Bluesea Cracker

2. Backstage

3. The Midnight Club

4. Big Fella Thanks

Hyperion, Tipster

1. Ballabriggs

2. Surface To Air

3. Character Building

4. Don't Push It

James Lawton, Chief Sports Writer

1. Oscar Time

2. Don't Push It

3. Tidal Bay

4. Niche Market