England defence coach John Mitchell says he "doesn't see any advantage" in opponents spying on training sessions.

On Tuesday, head coach Eddie Jones said someone was spotted filming from an apartment overlooking their pitch but refused to say who it might have been.

Mitchell appeared to point the finger at New Zealand before the World Cup semi-final with England on Saturday.

"If that is what they want to do, and that is the way they want to prepare, good luck to them," he said.

The former All Blacks boss added: "We just happened to be training where there are apartments above our tiny two-metre fence, so I am not sure about what the use of the tarpaulins are.

"The facilities have been excellent but it's an area where people live and there is the odd red light around. There was one up in the corner, which was a bit suspicious.

"It doesn't really worry me. This game is so dynamic now so I don't see any advantage in spying on a team."

Jones said it "might have been a Japanese fan" but admitted he "used to do it" himself, although stopped back in 2001, yet Mitchell believes spying is still common practice within the sport.

"When I took over the All Blacks in 2001 we had a manager who was highly military and he loved surveying the whole area," he said.

"To me, you can get too involved in it and create an anxiety in your group. There is enough pressure at this level without chasing around some blokes that might be in a building with a camera.

"I was with Sir Clive Woodward when we were going for a Grand Slam against Scotland and we chased somebody from one of the papers around the corner and caught him in a hedge.

"He was pretty unlucky actually but that was when the game was a lot different to what it is now.

"I've seen coaches spy, I've had other coaches spy. I've had mates spy as well, but I don't see any advantage."

'It's difficult to stay calm'

After Jones had talked up spying accusations, hyped the pressure on New Zealand and undercut expectation on his own team on Tuesday, normality was resumed in the England camp on Wednesday.

Just three days remain until England take on the All Blacks in Yokohama, bidding to reach their first World Cup final in 12 years against a team which has won the last two editions.

"The difficult thing is staying calm, staying collected," says open-side flanker Sam Underhill. "With any big game the sense of occasion is already there. I don't think it takes too much to get to another level, physically or emotionally.

"The difficult thing is making sure you peak at the right time, so you're not getting carried away in the week before the game - making sure that you stay clear and focused."

Jones will name his starting XV late on Thursday afternoon in Tokyo, with Underhill and his back-row partners Tom Curry and Billy Vunipola likely to be among the first names on his team-sheet.

At a time in the game's development when the battle at the breakdown has become ever more important - securing quick ball to fire your own team's attack, making an unholy mess of the opposition's to throw their patterns and timings off - the partnership of 23-year-old Underhill and 21-year-old Curry has been critical to England's four-match winning run.

In last weekend's quarter-final against Australia they subdued the much-lauded pair of David Pocock and Michael Hooper, the duo putting in a remarkable 36 tackles between them as England racked up a 26-point winning margin despite only having a third of possession and territory.

Four years ago all four World Cup semi-finalists were from the southern hemisphere. This time the split between north and south is an equal one, something Curry puts down to how teams from the Six Nations have changed their approach at the breakdown.

"I think the north is probably catching up," he said. "Teams, especially in the Premiership, are developing that style and bringing it to the international stage.

"The way that rugby is going, you see the benefits of that free-flowing game in attack and how teams try to slow ball down at the breakdown.

"Momentum is huge, and to be able to stop that speeding up is massive."

Underhill was part of the England team that pushed the All Blacks all the way in their last meeting, the single-point margin of victory hanging on a late try by the Bath man that was ruled out by the television match official.

England have not beaten the triple world champions since 2012, when a young team inspired by Manu Tuilagi and Owen Farrell handed out the second biggest defeat in All Blacks' history.

Underhill said: "It was a big opportunity for us, as is this weekend. But without sounding daft, it was just another game - which I think is key this weekend, treating it as just another game, otherwise we'll get carried away with the occasion.

"You can't artificially create belief in a group.

"We've been away for 120 days, with the pre-World Cup camp, the pre-World Cup games.

"Most of the group have been together for more than that now, so all the accumulated work together, understanding each other, knowing what each other is capable of - that's where that belief comes from.

"They're a very dangerous attacking side. They obviously like to play rugby in your half, so you want to keep them out of there.

"Discipline and cheap penalties will be an easy win for them and something you don't want to give them.

"If we do the things we're good at, and bring the best versions of ourselves, that's all you can really do.

"We all believe that if we do that there's no reason why we can't win."