It has taken 240 years, but Laura Mongan became the first woman to train the winner of the Ladbrokes St Leger as Harbour Law swooped late in another dramatic renewal of the world's oldest Classic at Doncaster.

After the drama of 12 months ago when Simple Verse won, then lost and was reinstated, everything looked pretty straightforward at halfway with odds-on favourite Idaho seemingly cruising.

However, just over three furlongs out as Seamie Heffernan angled for a run on Aidan O'Brien's colt, he appeared to take a false step, went down on his knees and fired his rider into the ground.

The race suddenly opened up, with champion jockey Silvestre de Sousa seizing the initiative on Richard Hannon’s Ventura Storm, but all the way up the straight he had the attentions of another O’Brien runner, Housesofparliament.

Having finally seen that one off, Ventura Storm had nothing left as Harbour Law, second at Royal Ascot over two miles in June, hit top gear under George Baker and won going away by three-quarters of a length.

The winner was returned at 22-1 and was also providing Baker with a first British Classic.

Thankfully Heffernan appeared to escape serious injury but was nevertheless taken to hospital as a precaution due to receiving a bang on the head. It meant he missed his ride in the Irish Champion Stakes at Leopardstown later in the evening.

Epsom-based Mongan said: “It was brilliant! I think I screamed a lot. I’m in shock.

“I’m so glad we came here and he’s proved that he can do it. We didn’t want to ride him like that, but George knows what he’s doing and all credit to him. We knew we could leave it to him.

“It was a really professional performance by the horse, we knew he’d go somewhere in life.

“It proves we can do it with the ammunition, it’s great to have a horse like this and bring him here for a race like this.

“It’s a bit surreal. I hope we are lucky enough to hold on to him.”

Describing her feelings when Idaho crashed out, Mongan said: “I started to worry for some reason.

“We’ll have to discuss what’s next, we genuinely haven’t thought about it.

“He’s not in at Ascot but he has an entry in France in October, the Prix Chaudenay.

“To go down in history as the first woman to win it is amazing, at least I’ve done something right.

“We’ve felt all along that whatever he did today, he’d be even better next year.

“It’s my daughter’s seventh birthday today but she’s at home with my mum along with my seven-month-old son. I’d promised her a party tomorrow and it might be a bit bigger now!”

Mongan is married to former jockey Ian, who won the Juddmonte International on Twice Over for the late Henry Cecil.

“I can’t get my head around it, we thought he’d run well but did we think he’d win? In a dream maybe, but he has,” he said.

“He’s the easiest horse to train. Henry Cecil said to me good horses make good trainers, and he is by far the easiest horse we’ve had to train.

“I’m so happy for Laura, the owners and Epsom. I’m going to enjoy this.

“I just pray he stays with us and he’ll be a lovely Cup horse next year.”

Baker said: “I can’t believe it, I’m so happy for Ian and Laura, they had so much faith in him and really deserve it.

“It’s an amazing feeling to win the Leger. I worked him at Kempton about two weeks ago and he felt brilliant.

“When Idaho clipped heels it made it a very open race.”

Hannon said of the gallant Ventura Storm: “I bought George Baker breakfast this morning and then he does that to me!

“All the way up the straight I thought we had it but we’ve been mugged. It’s unfortunate, but there you go.

“He had a very hard race there so I’d imagine that’s it for the season.”

Speaking from Leopardstown, O’Brien said of the Idaho incident: “It’s racing – there is no law. There are so many variables and that was one that you couldn’t think of happening.

“He put a foot on a divot and it just went away and it just unbalanced him. It’s just amazing. What were the chances of that happening?

“Séamus is on the way to get scans now, but he’s grand. I spoke to him on the phone. He said he was cantering.”

As for Housesofparliament, the Ballydoyle trainer said: “It was a little bit unfortunate when it happened as Colm (O’Donoghue) probably had to commit but he ran a good race.

“When that happens in a bunch of them a lot of stuff changes very quickly.”