London - Jason Roy says England's outstanding fielding display in their Cricket World Cup opener against South Africa set the tone for the hosts' bid to win the competition for the first time.

Eoin Morgan's side justified their status as World Cup favourites with a 104-run thrashing of South Africa at the Oval on Thursday.

Man-of-the-match Ben Stokes hit a confident 89 to keep England's innings on track, while three wickets from electrifying pace bowler Jofra Archer derailed the South African run-chase before they could establish any momentum.

But it was England's superb fielding that caught the eye as much as the contributions with bat and ball.

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Stokes pulled off a stunning one-handed catch to dismiss Andile Phehlukwayo on the boundary, with the all-rounder also involved in the run-out of Dwaine Pretorius.

England opener Roy admitted the team's flawless play in the field was a significant statement of intent as they set out on a six-week journey for World Cup glory.

Asked if it was the best England fielding effort he had been part of, Roy said: "It was. That was an incredible catch from Ben.

"As a collective it was very good. We pride ourselves on our fielding and we have been disappointed quite a lot with our fielding over the last year. 

"We've been incredible with the bat and ball but our fielding has sometimes let us down.

"The boys turned up and showed what we are about on the big stage and in the big game so we're really proud.

"It all gets logged and the analyst told us it was one of our best ever fielding performances."

Ranked as the world's top one-day international side, England are playing with the burden of great expectations as the host nation.

But Roy, who scored a composed 54 in England's 311-8 against South Africa, does not believe they will be fazed by the pressure as the tournament unfolds.

Next up for England is a clash with out-of-form Pakistan at Trent Bridge on Monday.

Pakistan were routed by the West Indies in their first match on Friday, but Roy will not be underestimating them. 

"There will be different threats. They've obviously got a great attack and it is going to be a case of going out there with the same game-plan and enjoying ourselves and trying to win a game of cricket," he said.