The 29-year-old has also been told he will bat at first wicket down, a crucial position that has not been satisfactorily filled since the days of Jonathan Trott.

In the past five Test matches Root, Moeen Ali and Ben Stokes have all started as the designated number three, while the use of a nightwatchman saw Keaton Jennings bat there in the second Test and Jos Buttler was publicly considered for the job too.

England have talked up the malleability of their team in Sri Lanka, emphasising the willingness of individuals to perform a variety of tasks, but a successful audition by Bairstow would lend a welcome air of permanence to the top order.

"One thing we all know about Jonny is whenever he's got a point to prove or is up against it, he generally comes out and does something pretty special," said Root.

"Hopefully we see that with Jonny this week – that determination and drive to really hammer that spot home for himself. It's an opportunity for him to try and nail that spot down and he's more than capable of doing it.

"At the minute that (keeping wicket) is not an option for him in this team and I think it's a really good opportunity for him to take his batting to another level.

"In the last couple of years he's been statistically one of the top 10 players in the world in Test cricket so it would be nice to see him really grab number three by the scruff of the neck and use it as an opportunity to start really consistently scoring big runs in this format.

"There's so many different combinations that we could go with that look extremely strong in all conditions.

"It would be, obviously, in terms of having a settled batting line-up, especially a top six – it would be ideal to get that settled down."

There are no concerns over how Stokes will take his move back down to number five after precisely one innings, of 19, in the top three.

Root indicated the all-rounder's workload with the ball, which could include new-ball duties this week in the absence of Curran and Anderson, meant he had a more natural home further down the card.

"I think that's his preferred position. Long-term as well, he's going to be bowling more in the English summer," he explained.

"Although it wouldn't be impossible for him – he's a very fit guy, very able to do so – it might be a better formula to have him in the middle-order.

"He is so valuable to this team and the white-ball team too, because he balances it out brilliantly. He is someone who always wants to be involved. He wants the ball, he wants to be bowling and he wants to try and influence what is going on in the field.

"They are the characters you want in the dressing-room and they drive standards. People look at them and say 'I want to be like that'. He's so valuable."

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