Marks and Spencer to begin selling boxes of 'double yolk' eggs

The special eggs are examined before boxing to check their yolk count

Around 0.1 per cent of eggs have double yolks in them (Rex Features)

A British retailer is to begin selling boxes of double-yolk eggs.

Marks and Spencer will start selling the packs of six free range eggs this weekend at £2.75 each.

Around 0.1 per cent of eggs have double yolks in them; the oddity is caused by a hormonal imbalance in young chickens.

The eggs for the special boxes will be sourced using a process known as “candling” – shining a bright light on each egg to show the silhouette of the yolks inside.

M&S product developer Ali Rodham said: “We're really excited to be selling double yolkers. We think they're cracking, and we're sure our customers will too.

“Perfect for people who think the yolk is the best bit of the egg, double yolkers are not only delicious, but they are healthy too.”

The yolk of chicken eggs is rich in vitamins B12, B6, A, K, E and folate; yolks are one of the few foods to naturally contain vitamin D.

Yolks are also rich in nutrients such as calcium, magnesium, potassium, sodium, selenium and iron.