Those comments were echoed by England defence coach John Mitchell, who said the final features the "two most powerful teams in the world".

Vunipola said: "South Africa are very big people but then again we have a few big blokes on our team."

Saturday's final is at 09:00 GMT in Yokohama.

'Little battle' of Vunipola v Vermeulen

England head coach Eddie Jones has previously said Vunipola can be the best number eight in the world, and the Saracens forward was influential in his side's victory over defending champions New Zealand in their semi-final.

But the 26-year-old has never won a Test match against opposite number Duane Vermeulen, who was equally impressive as South Africa edged past Wales in their semi with a dominant performance in the forwards.

"I've played against them a few times and he's got up so I'm going to try my best to win that little battle," Vunipola said.

"I played against him last summer and he was monumental in terms of getting them those two victories.

"He just played better.

"Not just me, but we've got to try and negate his influence."

Mitchell, who coached New Zealand in their semi-final defeat by Jones' Australia in 2003, says England must "earn" their victory over the Springboks.

"South Africa are strong and well coached and the gain line is going to be huge," the England defence coach said.

"They play in a particular way, but you must always be prepared for anything that comes at you. They have their own armoury and it's exciting.

"Against New Zealand we dealt with a lot of speed, a lot of footwork, but South Africa are certainly going to be a team that is more direct.

"Pressure is definitely going to come at us and that asks questions of your fundamentals."

However, Mitchell also said his side are "adaptable" and can play more than one way.

"We are really excited by the week," he added. "In reality, all we have done is present ourselves with another opportunity at the right end of the tournament.

"We want to get better and we feel we can get better as well. Everyone is really calm and eager to get on to their work."

'Honoured and delighted'

Jerome Garces will referee the final, becoming the first Frenchman to officiate in the sport's showpiece event.

World Rugby announced the appointment on Tuesday of the 46-year-old, who has refereed 55 Tests, including 11 World Cup games.

World Cup final referee Jerome Garces will retire next year

The Springboks will hope there is no omen in the fact Garces was in charge for their most embarrassing defeat - the shock defeat by Japan in a World Cup pool game in Brighton four years ago.

However, the Frenchman was also in charge for their most recent Test victory over Wales in the last four.

"I am honoured and delighted to be appointed to referee the Rugby World Cup 2019 final," Garces said.

"It is a dream as a referee."

Garces has enjoyed a glittering final year of his career after he refereed the European Champions Cup final between Leinster and Saracens in May, as well as the French Top 14 final between Toulouse and Clermont in June.

He has shown a total of six yellow cards at the tournament so far but has not sent off anyone.