O'Brien says it is England's fight that has really impressed him.

"Their record speaks for themselves, they've been a very good side and a difficult side to beat.

"They've been in some tight scraps and came out the right side of them."

Meanwhile, England full-back Mike Brown says they can't wait for Saturday's game with Ireland.

"We're massively excited. You can see it in the guys, you can hear it. Everyone's just really excited about the weekend."

Victory in Dublin for Eddie Jones' side would be a record 19th straight win, as well as the securing the Grand Slam.

England are also exploring the possibility of staging a mouth-watering showdown against New Zealand this autumn.

In a frustrating quirk of the international schedule, the game's top two teams are not scheduled to meet until late next year, but it is understood that November 4 is now being examined as a possible window for an additional fixture.

If England beat Ireland on Saturday they will break the All-Blacks record for consecutive wins.

"We are scheduled to play New Zealand in 2018 and if an opportunity came up to play them before then we would pursue it," an RFU spokesman said.