George Ford said "greasy" conditions made it tough for England to break down Japan during the first half of their 34-12 win at the Rugby World Cup.
On a humid evening in Nice, both sides opted to kick the ball and keep it tight in the opening 40 minutes before England scored three second-half tries.
Japan made 14 handling errors in the Pool D match, while England made 11.
"It was probably not the prettiest to watch but it's hard to play with the ball in these conditions," said Ford.
"These late kick-offs are dead greasy but we got there in the end.
"There was some improvement from us tonight but you can't underestimate how difficult it is to play in those conditions.
"It doesn't look like it from the TV or the stands but I promise you it's very difficult. It was sweaty and clammy and you have got to be really clever in the way you play - and more often than not, we made the right decision.
"We knew it was going to be tough and Japan challenge you in different ways. We knew it would be that third or fourth quarter we could pull away a bit but we are delighted to get the win."
England's first try, through Lewis Ludlam, came after Japan spilled the ball and failed to reclaim their own line-out, and Courtney Lawes scored their second when the ball went backwards off Will Stuart's hand and fortuitously ricocheted off the head of Joe Marler.
That ended the Japanese challenge before Ford, who contributed 14 points from the boot, picked out Freddie Steward for the third try with a pin-point cross-field kick.
Joe Marchant's powerful finish late on sealed the bonus point as England wore down their opponents.
'We still have a lot of growth in us'
"We knew we would get the rewards if we kept doing the right things," said England coach Steve Borthwick.
"The players have got to find a way to get the result. You saw a Japan team who kicked the ball 37 times, which is unusual and tells you a lot about the conditions tonight.
"You can feel the ball spinning out of your hands even before you've made contact. It's hot, humid, it makes for a wet-weather game.
"The players found a way of scoring four tries. We felt that last quarter was where we needed to accelerate and the boys did that.
"We still have a lot of growth in us. Players of quality are going to start coming back. Owen Farrell becomes available next week [after suspension]. Tom Curry will become available the following week.
"I said the team is preparing for the tournament, they have immense quality throughout it, they want to perform on the biggest of stages and the boys showed that tonight."
A second victory in as many games for England moves them into pole position to qualify for the World Cup quarter-finals from Pool D.
'Good to see England scoring tries' - Ashton
Former England wing Chris Ashton told BBC Radio 5 Live that England's kicking gameplan was effective.
"It was good to see England scoring tries and it was a good way to finish the game," said Ashton. "It seemed the ploy was to wear Japan down with the kicking plan in the first half, however frustrating it may have been.
"It was tricky out there, as we have seen in all the games. It was very hot and sweaty which makes it very difficult."
World Cup winner Matt Dawson said "there was a lot to be really positive about".
"I loved the way England came out in the second half and upped the tempo," he said on Radio 5 Live.
"The Japanese had some good chances and had they scored you go into a different mindset, but England defended brilliantly.
"It was an efficient performance and sets up England beautifully for the rest of the pool stages and into the quarter-finals.
"That's as complete a performance I have seen in Borthwick's tenure."
England face Chile in their next game in Lille on Saturday before finishing the pool stage by playing Samoa on 7 October.
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