The National's real outsiders: sisters-in-law hoping to upset the odds in a man's world

It was Ginger McCain, the mastermind behind Red Rum's hat-trick of victories in the world's toughest steeplechase, who ventured only seven years ago that "horses do not win Grand Nationals ridden by women".

But today the legendary trainer could be proved wrong when two women line up at Aintree with realistic hopes of shattering one of sport's biggest bastions of male supremacy.

Nina Carberry and Katie Walsh are not just National Hunt's leading female exponents, they are also sisters-in-law and this year were at the altar as bride and bridesmaid for a union that brought together Ireland's top racing families.

The twin dynasties will field four riders today. Their brothers, Paul Carberry and Ruby Walsh, both previous winners, will also be on the starting line.

But though the men's mounts may prove a safer bet in the hard-to-predict race, the National Velvet dream of a woman triumphing over Liverpool's 40 fences is already firing the imaginations of the once-a-year gambler.

Yet Ms Walsh, the slight favourite of the women, said that while victory would be a "dream come true," she was realistic about her chances. "I would just love to get round, that's the main thing, it's my first ride in the Grand National and loads of jockeys have ridden in it who have never even got round."

Since 1977 when women were first allowed to ride, 14 have taken part but only four have gone the distance. Yet William Hill is offering odds of 11-1 on a women winning today.

The friends have met before. Ms Walsh triumphed at Cheltenham in 2010 narrowly beating Ms Carberry although both were later given bans for excessive use of the whip. They are determined and committed competitors. Following her Co Meath wedding to Ted Walsh Jnr in February, Ms Carberry spent just two days on honeymoon before preparing for Cheltenham.

Gee Armytage, a two time winner at Cheltenham and personal assistant to 16-times champion jockey Tony McCoy, said she was confident a woman would win at Liverpool soon, if not today. "It is only a matter of time before someone gets on the right horse. There is no reason why Nina or Katie should not win," she said.

Alison Lidderdale, of Women in Racing, which promotes female success in the sport, said there were surprisingly few vestiges of sexism remaining. "These girls have come up through the ranks and battled hard to be where they are. In the weighing room they are completely respected," she said.

And they're off! The women in the saddle

Nina Carberry The 27-year-old from Co Meath will be on 20-1 shot Organised-confusion. In 2011, she became only the second woman to win the Irish Grand National. She is regarded as one of the toughest contenders in the sport. Recently married Ted Walsh Jnr, brother of Aintree rival Nina, who was a bridesmaid at the glitzy bash. Carberry is from one of Irish racing's most famous families. Both her brothers are jockeys; her father Tommy is a top trainer.

Katie Walsh Slightly favoured to become the first woman to win the National on 16-1 Seabass. Hails from one of Ireland's great jumping dynasties. Her father Ted trained 2000 National winner Papillon, ridden by her brother Ruby. Mr Walsh Snr chose his daughter to ride Seabass after she won twice on the horse this season. Katie, 27, began her amateur career in 2003 but proved her worth in 2010 when she bagged two winners at the Cheltenham Festival.