Millions of people are expected to have a flutter on the 166th John Smith's Grand National today.

Forty runners and riders will compete in the world's most famous steeplechase at Aintree Racecourse.

A sell-out crowd of more than 70,000 in Liverpool will be joined in watching the contest by an estimated 600 million television viewers across the globe.

Bookies hope the betting could top #150 million with punters expected to wager more cash than usual as this year's race is the only major sporting event of the weekend.

The Grand National usually coincides with the US Masters and FA Cup semi finals.

Coral Spokesman Simon Clare said: "The Grand National is one of Britain's most popular sporting occasions, with two thirds of the adult population likely to place a bet.

"Despite concerns raised over the safety and welfare horses in the race, the Grand National is as popular and ever, and while the racing authorities have rightly taken action to ensure the race is as fair and safe as possible for horse and rider, betting turnover on the world's greatest horse race is expected to top #150 million for the first time.

"Seabass is expected to be the best backed horse in the race, as the so-called housewives' choice, given the huge media spotlight on his rider Katie Walsh who is bidding to be the first lady rider to win the Grand National."

There will be huge focus on Ms Walsh and her family in this year's race.

She sparked controversy ahead of the meeting when she defended the sport from accusations of cruelty and said the horses were treated better than "many children".

Her brother Ruby, who won the Grand National with Papillon in 2000 and Hedgehunter in 2005, is also a favourite for today's race riding On His Own.

In a further twist their father, Ted Walsh, trains two of this year's runners, his daughter's horse Seabass and Colbert Station, the mount of champion jockey Tony McCoy and another of the bookmakers' favourites.

William Hill is offering 40-1 on a Walsh 1-2-3 involving Colbert Station, Seabass and On His Own to fill first three places in any order.

The Grand National is worth #975,000 in prize money, making it one of the richest jump races in Europe.

It will be the first time the contest is broadcast in the UK by Channel 4, after the broadcaster won the rights to show the meeting for the next four years.

Two horses have also died during this year's meeting.

Little Josh fell during yesterday's Topham Chase, which is run over the Grand National fences.

The 11-year-old, ridden by Sam Twiston-Davies, suffered a broken shoulder and was later put down by veterinary surgeons, Aintree said.

It followed the death of Battlefront after he was withdrawn during Thursday's fourth race by his jockey Katie Walsh.

Animal rights groups have called for people to boycott the broadcaster and shun the race in response to concerns about the horses' welfare.

Four horses have died in the last two Grand Nationals and this year Aintree replaced its wooden fences with new, plastic fences designed to be "kinder" on the animals.

A protest will be staged outside the racecourse today by members of Fight Against Animal Cruelty in Europe (Faace).

Chairman Tony Moore said: "Unfortunately it is to be expected that horses will come to harm and die in this year's Grand National.

"There is no way you can make a race like that horse-friendly and safe."

Tomorrow's weather on Merseyside is expected to be much improved as biting winds, which marred the first two days of the meeting, ease off and temperatures rise.

Laura Caldwell, a forecaster for MeteoGroup, the Press Association's weather division, said: "The drop in wind will make a considerable difference on Merseyside and allow for temperatures of 10C (50F).

"There's little chance of rain either so it seems the Grand National has saved the best of the weather until last."