A rare complete egg of the long-extinct elephant bird has sold for more than double its estimate, fetching €51,031 at a London auction.

The creature is believed to be the largest-ever bird and the specimen sold by Christie’s in London is reckoned to be pre-17th century.

The partly fossilised egg – which had been valued at between €15,309 and €22,963 before the sale – is 100 times the average size of a chicken’s egg. It is 30.5cm high and 22.2cm at its widest point.

It was one of the most celebrated lots at Christie’s travel, science and natural history sale.

The elephant bird looked like a heavily-built ostrich and grew up to 3.35 metres in height, but is believed to have been hunted to extinction between the 14th and 17th centuries in Madagascar.

Although fragments can be found on the island, intact specimens are said to be extremely rare.

The sale figure includes the buyer’s premium.