Joe Root admits England can no longer afford to play their best cricket with their backs against the wall after South Africa snuffed out hope of another outrageous fightback from his side in the Boxing Day Test.

England arrived in Centurion on Sunday needing to scale a mammoth target of 376 but were rounded up for 268 as their latest attempt to upset mountainous odds came undone at the hands of a relentless Proteas attack.

There would be no third act to Ben Stokes' magical 2019, with the elation of his knocks at the World Cup final and the Ashes Test at Headingley replaced by a messy dismissal for just 14 and a chastening 107-run defeat.

England have earned a reputation for fighting hardest when cornered – they won a dead rubber against the West Indies in St Lucia back in February, beat Ireland after being bowled out for 85 in July and then penned their record run chase against Australia in Leeds – but Root wants more.

The tourists allowed South Africa to make 284 despite tumbling to 111 for five after Root won the toss and then lost seven first-innings wickets for 39 to make just 181 in reply.

Their response to what ended up as a lost cause showed enough guts to leave the hosts nervous at times, but Root would prefer to see his team leading from the front.

"I think the thing that's frustrating me is that, when we find ourselves behind in the game, we show a lot of character, fight and determination and we find ways of getting ourselves back into things," he said.

"In terms of character over the last two days, I can't fault anyone. We turned up today with real belief we could win the Test. Even at lunch me and Ben looked at the scenario and it was the same equation as Leeds not so long ago.

"But we need to do that at the start, get ahead of it. When we get the opportunity to turn the screw, we really need to take it, both with bat and ball. That's where the game was won and lost this time round, the first innings with bat and ball."

Root did not use the bug which was spread through the camp as a reason for defeat, though nor did he downplay the effect it has had on preparations.

He fell ill and was forced into quarantine as the game drifted further away from England on day three, with another nine squad members and four backroom staff suffering symptoms since arriving in Johannesburg a fortnight ago.

Three were ruled out of the Test entirely and others went in light on workload. With five days to go before the second Test in Cape Town, Root simply hopes for an end to the medical bulletins.

"We're not going to hide behind that as an excuse, but 14 of our squad have been taken ill in the last week and a half," he said.

"We've had a lot thrown at us and everyone has dealt with it the best you can. It's frustrating, but it's happened.

"Hopefully the illness is through the camp and we can all be fighting fit in time for Cape Town."

England have asked Somerset pair Craig Overton and Dom Bess to stay on for the trip to Newlands, with both men initially called up as cover, and Bess, in particular, has a real chance of adding to his two caps.

Another potential selection debate involves decorated seam pair James Anderson and Stuart Broad, with some pundits suggesting the veteran duo should no longer play together despite sharing more than 1,000 Test wickets.

"If difficult decisions have to be made down the line then they will be, but if they don't then they won't," said Root, equivocally.

"It would be silly to push fantastic experience and a wealth of knowledge of fast bowling out the door when there is no need to. You don't want to wish those guys away or look back and think, 'We've forced Jimmy Anderson out'. You look at him physically and he's in fantastic fettle and he's got a brilliant record in these conditions. Similar with Stuart.

"It' s a fine balance, you've got to look at the surface and at an attack you feel is best going to counter that and best counter the opposition you come up against."