Alastair Cook's urgent attention must remain on the Royal London series, but he is enduring some anxious moments too about Matt Prior's readiness or otherwise for a Test return next month.

England's established Test wicketkeeper has been prevented from restating his case, after being dropped mid-Ashes, by an Achilles injury which has restricted him to just two first-class matches this summer - both at the beginning of April.

Plans for the 32-year-old to return in Sussex's LV= County Championship Division One match against Middlesex at Northwood were dashed by a washout.

It was decided - even before no play proved possible on the final day - that he would be better served undertaking wicketkeeping drills with England's specialist Bruce French.

That has proved fruitful, with Prior tweeting: "Hard session with frenchy today, as always, and so far the injury has responded very well!"

Prior is expected to be back instead for Sussex's NatWest T20 Blast match away to Glamorgan on Friday night, although it is not yet clear whether he will keep wicket or play only as a batsman.

Either way, time is worryingly short for him to prove his fitness - and form - before England name their squad late next week for the first npower Test against Sri Lanka at Lord's on June 12.

Cook, whose one-day international team currently lead their series against the same tourists 2-1 after a much-improved performance at Emirates Old Trafford on Wednesday, acknowledges the Prior issue is a pressing one.

"It is a big concern," he said.

"I've been speaking to him every week, and he's been doing everything he can.

"He's incredibly frustrated, because Achilles injuries are hard to heal.

"He's a big part of our plans, but we can't rush a guy back. That wouldn't be fair on him or to the England team."

Prior made his debut, at Lord's, in Peter Moores' first Test as coach back in 2007 - marking the occasion with a century, one of four in England's first innings against West Indies.

Seven years on, Prior's old Sussex coach Moores is back for his second stint following England's major management reshuffle after their Ashes whitewash last winter.

It would therefore be fitting if Prior managed to make the rendezvous at HQ.

Cook added: "There's time, about two weeks to the first Test, and we'll be in constant communication throughout.

"He knows he is a big part of things, and we want him to be there. But if he's not there, it will give someone else an opportunity."

Of those, England's limited-overs wicketkeeper Jos Buttler appears to be first in the queue.

He is uncapped at Test level, but is thought to be significantly ahead of current incumbent Jonathan Bairstow - who replaced Prior for the final two Tests Down Under.

Cook is taken by Buttler's potential, but admits the 23-year-old is still honing his skills behind the stumps.

"Like a lot of guys, he is a really talented wicketkeeper and a really talented cricketer," said Cook.

"He's nowhere near the finished article with his wicketkeeping. But just watch him practise - you will see him put the hard yards in - and that will keep going the right way, no doubt."

Cook's ODI team, meanwhile, put the horror show of Durham behind them by bowling Sri Lanka out for just 67 - thanks to Chris Jordan's career-best five for 29 - on the way to a 10-wicket win on Wednesday.

They will therefore arrive at Lord's on Saturday 2-1 up with two to play and on the verge perhaps of delivering the first series victory of the new era.

Cook is prepared to accept some mitigation for the patchy performances to date, but not too much.

"I think we'll have some inconsistency, but I'd hope they won't be as bad as what we showed at Durham," he added.

"There is no need for that - you can't blame that on inexperience at all.

"It wasn't pretty viewing.

"There will be some inconsistency with the less experienced guys, but that doesn't mean you can pass off every poor performance on that."

Within three days, however, England were back on track.

"There weren't so much harsh words, but the 11 guys who played knew they'd let themselves down with that performance," said Cook.

"What it did show against a side like Sri Lanka is that if you give them an inch they will take a mile.

"It was an okay score, but as soon as they got a sniff of a victory they jumped in hard.

"It was a realisation to the guys that after one good performance, you have to keep going at 100 per cent or you get found out."

It was Sri Lanka who discovered that in Manchester.

Cook added: "As a sportsman, you have to spend your time ... looking at the next challenge and bouncing back from the bad stuff.

"I think we caught Sri Lanka napping a little bit.

"We were out of the blocks straightaway."