England are in an "unbelievable place psychologically" and would not fear playing anybody, according to Sky Sports expert Will Greenwood.
Eddie Jones' side completed a perfect calendar year on Saturday with a 37-21 victory over Australia to make it 13 wins out of 13 in 2016. The result also saw England equal their record of 14 straight wins.
Australia had raced into an early 10-0 lead at Twickenham and were 16-13 in front at half-time before England turned on the style in the second half and Greenwood hailed their ability to adapt on the move.
"To go in [at half time] as the second best team and to come out of it and win it 37-21 and be all over Australia at the end of the game is a real testament as to how far they have come in terms of the removal of that horrible word in sport 'doubt'," said Greenwood on Sky Sports' Facebook Live.
"Unbelievable place psychologically is my final note. What I mean by that is now they don't doubt themselves in any way, shape or form. Eddie was saying that he'd like to play New Zealand tomorrow and this is the transformation, not one of those England players would walk onto a field against the All Blacks now believing in anything other than an England win."
In the build up to England's final autumn Test, former centre Greenwood spent time at Pennyhill Park and felt first-hand the atmosphere and unity among the current squad.
He added: "I had a great day down at England training last Tuesday. I put my boots on and ran around with them and just the small talk and the chat, you could have closed your eyes and gone back 15 years ago thinking that this is a team destined to do something really, really special."
Should England complete another Grand Slam at next year's Six Nations, Jones' side would surpass New Zealand's record of 18 successive wins by a Tier One nation.
However, Greenwood says the players' main focus is on success at the 2019 World Cup in Japan.
"All roads for Eddie lead to Tokyo, everything that they talk about is getting better, making sure that getting better doesn't stop and that restlessness and search for continuous improvement is right through the heart of that team," explained Greenwood.
"When they look back in 20 years time a world record will be nice, a back-to-back Grand Slam will be nice. But, if you speak to players that have gone to World Cups as favourites and don't win and you ask them the thing that they remember about their sporting career and it isn't a run of 18 games, or back-to-back Grand Slam. It's when it [a Rugby World Cup] came around and they missed their shot. That's what drives these players [to not feel that].
"Records will come and go, Grand Slams may come and go but there's only one thing that Eddie will judge on and one thing that these players will judge themselves on. They've now put themselves into a position to have a crack at Tokyo and have a crack at winning the World Cup."