South Africa full-back Percy Montgomery admits he will not be surprised if Tonga send England spinning out of the World Cup on Friday.

The world champions meet the Tongans in a winner-takes-all qualification decider in Paris, and Montgomery is perfectly placed to judge their relative merits.

The full back booted 18 points in the Springboks' 36-0 thrashing of Brian Ashton's men.

On Saturday he came off the bench, along with a number of other South African big guns, to help rescue his team and secure a hard-fought 30-25 win over plucky Polynesians.

There is no question which of the two Pool A teams gave the Springboks the bigger test.

Even though England go into the crunch clash as favourites, Montgomery believes Tonga have every chance of causing an upset.

He said: ''You can never write off the big teams like England because they have so much experience and they have the back-up.

''I think it will be tough for them. The Tongan team have got some good momentum at the moment, they've got some really good players.

''It wouldn't surprise me at all if they were to win. They have had a great World Cup, they are playing attractive rugby and it's a strange game.

''We needed all our composure to beat them and England will find it hard.''

The Springboks were 10-7 down to Tonga heading into the final 30 minutes of a pulsating clash in Lens, and it was only then that coach Jake White brought his cavalry off the bench.

John Smit, BJ Botha, Victor Matfield, Bryan Habana and Francois Steyn all went on.

They helped turn the tide and when Ruan Pienaar went over for his second try of the day, in the 65th minute, they had a 27-10 advantage.

The Pacific Islanders, whose tough-tackling and charging runs caused their opponents problems all game, fought back manfully and came to within five points of the 1995 world champions with eight minutes left thanks to tries by Sukanaivalu Hufanga and Viliami Vaki.

A final, match-winning score eluded them, despite South Africa being down to 13 men at one point, but Tonga left the field after the final whistle to vibrant applause for the crowd.

''Playing against the Islanders is always tough,'' Montgomery added. ''A lot of the Tongan team play overseas. They played with passion, they defended very well and attacked very well.

''It is always good to have a Test like this, it brings you back down to earth a bit. Obviously we wanted a bigger score but this is Test-match rugby."

The bonus-point win capped a perfect day for Montgomery, who claimed his 90th cap and broke the national appearances record he had been sharing with legendary scrum-half Joost van der Westhuizen.