Seagrave laid down a time of 5:10.960 for the rest of the field to beat but her challengers fell by the wayside owing to a combination of crashes and bad luck.

Myriam Nicole of France looked on course to beat the British rider but a crash in the second half of her run meant she could do no better than silver.

She eventually finished in nearly nine seconds down on Seagrave.

A similar fate befell Atherton, who topped qualifying yesterday, as she snapped her chain out of the gate before also suffering a crash.

Atherton, backed by a raucous home crowd, recovered valiantly to secure third place in 5:20.016.

The victory for Seagrave came after she finished some way off the pace in qualifying yesterday.

The Briton said she was in tears all morning after her qualification performance and also shut off social media in order to focus on today's final.

"I had a decent run and didn’t really perform to what I expected," said Seagrave.

“I’ve had the worst week I possibly could. 

"I’ve turned my phone off, shut off social media and this morning was horrible.

“In previous years, I was out for a year with a dislocated elbow and I’ve had horrible injuries in the past.

“To finally just get down in one piece was going to be the goal, let along taking the win - that’s just a bonus.

“I never thought it would happen - honestly.”

There were also plenty of thrills and spills in the men's race as Amaury Pierron led home a French one-two with a time of 4:34.452.

Pierron's compatriot Loris Vergier took silver and Australia's Troy Brosnan did enough for bronze.