A six-year-old boy in Britain has found a shark tooth belonging to a giant prehistoric megalodon that could be up to 20 million years old.

Sammy Shelton found the 10cm-long (4in) tooth on Bawdsey beach in Suffolk. It has been confirmed as belonging to a megalodon – the largest shark that ever existed – by expert Prof Ben Garrod, according to BBC News.

The boy’s father, Peter Shelton, sent photographs of the find to Prof Garrod, a broadcaster and evolutionary biologist at the University of East Anglia in Norwich.

"It belonged to a megalodon, the largest ever shark – and its teeth are not often found around the UK coastline," BBC cited the expert as saying.

The megalodon could grow up to 18m (60ft) in length, scientists estimate, and weigh up to 60 tonnes, he said.

“Dwarfing anything else swimming in the waters at the time, these were "specialist whale eaters,” Prof Garrod said.

The megalodon was a carnivore and had no known predators

It could eat anything it liked, but its favourite food was whales

Most of this shark's hunting was in the open sea and it attacked its prey near the surface, when it came up for air

Lived from about 20 million years ago, long after the dinosaurs became extinct 65 million years ago.