Photographs of a cloud formation have confounded weather experts who say they have never seen anything like it.

Francesca Bregdan was standing in her garden in Bradwell, near Great Yarmouth, when the striking shape caught her eye.

But it wasn't until more than a year later that she realised its rarity.

Her research revealed the formation to be a rare "double helix" last publicly reported in Russia in 2012.

The 31-year-old graphic designer, who has a passion for nature and photography, said she was keen to find out more about how it was formed.

Zoe Johnson, a forecaster at Weatherquest based at the University of East Anglia said: "I would say none of us have seen anything like it before - and between us we've looked at a lot of cloud pictures.

"The consensus from us is that it’s cirrus cloud that has been twisted, perhaps by some upwind topography.

"A theory from one of my colleagues is that it could be cirrus spissatus, which often originates from the upper part of a cumulonimbus cloud.

"Cirrus clouds are the highest of the main cloud types, usually made up of patches or bands of ice crystals."

She added that although a helix was not an official cloud type, the pictures could be said to show a helix composed of cirrus clouds.