We don't usually talk about Harry in the Tenner Bet household.

We have done this week, though. Harry was Mrs Tenner Bet's first beau. He was blond, statuesque and feared nothing and no-one. In contrast, I am stocky, hairy and a craven wastrel.

Imagine my predicament, then, when Mrs Tenner Bet started talking about the Grand National. She hates horses and gambling almost as much as I hate being told I'm a craven wastrel. "Will you back a horse for me in the National?" she asked. "Yes," I said. "Which one?" "Harry The Viking," she replied, counting out the pound coins from Wee Fiver's piggy bank as she did so. Her answer winded me. "It'll never win," I retorted. "Oh, here we go," she continued. "No," I said, "it will not win the Grand National this year or any other." "But the whole thing is a lottery," she hit back.

"Aha, well, that's where you are wrong," I replied. "That's the last thing the National is and I'll prove it. There are at least four ways to half the field at a pen stroke. And here's how."

10 CHASE RUNS

Poor old Harry doesn't even make it over the first hurdle. He is the type of runner picked only because his name reminds the once-a-year gambler of their son-in-law, brother or, dare I say it, first boyfriend. Horses that win the National – including 10 of the last 10 – almost always have had 10 races over fences. This is a big negative for the buzz horse On His Own and hence I'll be swerving Willie Mullin's favourite which can be backed as short as 7/1. The same stat does for the well-fancied Cappa Bleu and Colbert Station. Lost Glory is another to fall by the wayside.

11ST 6LBS OR LESS

National winners run for more than four miles so obviously the lighter a horse is, the better its chance. Weight is becoming less significant as evidenced by the number of winners (four from five renewals) that have been in the 11st-11st 6lb range. I'll stick to the upper end as a dividing line, though, and we lose four as a result, including another near the head of the market – Imperial Commander – and What A Friend.

3 MILE WIN, £17K WIN

Another key trend and one that seems to be ignored when Seabass is discussed. If a horse has never won over three miles it's asking a hell of a lot for it to do so over four.

National winners also tend to have won a race worth at least £17,000.

The two trends together claim another six from the field.

OFFICIAL RATING

The official rating mark over a 10-year sample reveals only horses in the 138+ bracket should be considered. I've widened it to cover those from 135+. By the time all of the above trends are applied we're left with 15 contenders.

THE METHOD

By attributing scores to the key remaining trends – which include variables such as at least three chase wins, a run over hurdles during the season, Racing Post ratings, Irish breeding, age, time off the track and size of fields in which chases have been won – we can cut the list by more than a half again.

The longlist shows seven with key profile stats – some with question marks and others that fit the profile spot on and those are: Teaforthree, Chicago Grey, Big Fella Thanks, Joncol, Rare Bob, Sunnyhillboy and Ballabriggs.

Taken in isolation Teaforthree looks the perfect type for this race, jumps superbly and stays all day.

Chicago Grey was well fancied for this race last year when brought down through no fault of his own.

Big Fella Thanks has been there or thereabouts before but he's up in the weights and it's unlikely he will better his fourth place of 2010. Joncol has doubts over stamina,

Rare Bob is 3lbs lighter than he was last year and form has been an issue this season although his recent third at Naas gave cause for optimism. Last year's second, Sunnyhillboy, is 10lbs worse off this time and while he was caught on the line in 2012, his Cheltenham Festival appearance was cited as a reason for his agonising defeat. It's hard to favour him for the win but he could go close again. Finally, Ballabriggs, the 2010 winner, has a solid case for e/w claims.

THE BET

I can't look past Teaforthree (16/1) but it requires forgiving him his last effort when he was beaten by 43 lengths. Otherwise, he ticks every box. Chicago Grey (14/1), Sunnyhillboy (20/1) and Ballabriggs (20/1) make up the other places. At those prices, I'm going each-way on all four but make sure you shop around for bookies paying places 1-5.