The 20-year-old will join up with last year’s beaten Premiership finalists at the end of the season from Championship side Bristol.

Vunipola enhanced his reputation as one of England’s brightest front row talents by helping the Red Rose youngsters claim the U20 Six Nations Grand Slam this year.

The New Zealand-born front rower was thought to have been pursued by a number of suitors including Bath but Vunipola admitted the offer from Saracens was impossible to turn down.

“I have enjoyed my time at Bristol, but the opportunity to join one of the top clubs in the country is very exciting," he said.

“From the unity and spirit within their squad, from the unique way they look after players and families, and from the way they are developing so many young English players, everyone can see there is something very special happening at Saracens and I am looking forward to being part of it.”

Vunipola will join England U20 team-mate Owen Farrell at his new club and director of rugby Mark McCall has tipped him for the top.

“Mako is already rated as one of the outstanding players of his generation, and he has been actively pursued by many Premiership clubs,” he said.

“We are delighted he has chosen to join Saracens, and we look forward to helping him fulfil his immense potential, on and off the field.”