A normal-sized hen has laid what is believed to be Britain’s largest egg.

BB, a three-year-old black maran, produced the monster egg, which is four times larger than a standard egg, last week.

It measures nearly eight inches in circumference, is 3.75 inches tall and weighs 200g.

It was discovered by owner Alison Savidge, 51, who couldn’t believe what she saw.

The bookmaker and mother-of-two said: “I own three chickens and last week was shocked to find this egg had been laid by one of them.

“I originally thought it must have been a goose or duck egg it was that large.

“I definitely think it must be a contender for one of the largest eggs laid in the UK.”

Alison lives in her three-bed detached home in Peterborough, Cambs with her husband Andy, 48, and two daughters Hayley, 24, and Charlotte, 21.

The family have had chickens for around five years and revealed that BB is a “temperamental” layer.

In the weeks before producing the massive egg she’d only been fed her usual diet of corn and acted normally, they revealed.

Describing the day she found the egg, Hayley, also a bookmaker, said: “My mum was a little bit confused and ended up coming up to the house and getting me to come and see it because she was a little bit shocked.

“I went down and we didn’t know what to make of it. When my dad came home he was just as amazed.

“We don’t know what do with it. We don’t want to break it because it’s so rare but we’re all convinced it’s a double yoke. I guess we’ll never know.”

The family are planning on doubling the size of their current brood by adding another three chickens in the coming weeks.

The Savidge family’s egg beats previous contenders for the prestigious crown including a hen which laid 194g egg in York in March 2013.

The lay coincides with National Egg Week which ran from Monday to Monday October 17.