England are "three or four years" from hitting their peak, says Six Nations Grand Slam-winning coach Eddie Jones.
Jones believes his side "will only get better" after they beat France to win a first Grand Slam title in 13 years.
The Australian, 56, replaced former boss Stuart Lancaster in November after England failed to reach the knockout stages of their home World Cup.
He told BBC Sport: "The average age of this squad is 24, generally in trophy-winning teams it's 28 in Test rugby."
A 31-21 win over France in Paris on Saturday saw England win the Grand Slam for the first time since 2003.
"It's a great achievement and I always had confidence in them," said Jones.
"I'm very proud of the boys. We were not at our best but we battled throughout and deserved the victory."
'All down to Eddie'
Jones brought in Dylan Hartley to replace Chris Robshaw as England captain and praised the efforts of both players, as well as other experienced members of his squad.
"Dylan Hartley has been fantastic," said Jones. "Billy Vunipola, Mike Brown and Owen Farrell have done very well assisting him, along with James Haskell and Chris Robshaw. That nucleus has been very strong."
Sir Clive Woodward, who coached England to victory in the 2003 World Cup final against Jones' Australia and was in charge for England's last Grand Slam success, tweeted his congratulations.
He posted: "Massive night England & congrats to Eddie and his team, totally deserved and all down to Eddie, just the start for England."
However, Jones insists his contribution accounted for "less than 10%" of England's 2016 triumph.
"The players have done a lot by themselves, all I've tried to do is create a good environment for them," he added on Radio 5 live's Sportsweek programme.
"When we lose, I get 100% of the blame and that's right. When we win, the credit should go to the players and that's 100% right.
"They worked things out on the field really well by themselves."
What next for England?
Jones' side will visit Australia in June, facing the Wallabies in Brisbane (11 June), Melbourne (18 June) and Sydney (25 June).
It is the first time the countries will meet in a three-match Test series.
The former Japan boss says England must improve if they are to win all three Tests, but is confident his side have a chance
"It's going to be like bodyline cricket, we've got to get out there and get stuck into them. If we do that we give ourselves a chance."
When asked how England would fare if they had to play Australia, New Zealand and South Africa, Jones replied: "I reckon at this stage we could definitely win two of them, and that's not good enough. We need to be able to win three of them."
'We wanted to be the most dominant team'
Inside centre Farrell told BBC One: "It's brilliant. We set ourselves a goal to be the most dominant team in Europe and we've achieved that.
"This squad has been brilliant since we met up at the start of the Six Nations. I'm just chuffed for the boys, we have a few that have been through a lot."
Saracens' Vunipola said that the failure at the World Cup was still on the players' minds, but added he was delighted with England's Grand Slam.
"This means a great deal," said the number eight. "It's such a great bunch of guys and we've had a great eight weeks.
"No-one can forget the World Cup but this is a great achievement and I'm so happy at the moment."