England showed real improvement in Sri Lanka - Jonathan Agnew

England's Jos Buttler (left) and Joe Root (right) applaud the fans as they walk from the field following third Test victory over Sri Lanka
England recorded their first away series win since beating South Africa in 2015-16

I played in Sri Lanka, so I know how hard it is to come here and win.

The weather is baking hot and the conditions are alien to English cricketers. Therefore, England's achievement of securing a series whitewash in three back-to-back Tests is a significant one.

The bare facts highlight the rarity of the result. Only twice before had England secured an away whitewash in a series of more than two Tests. In the past two years, Sri Lanka have beaten Australia 3-0 and South Africa 2-0 on home soil.

When you add the context that, on their last tour of the subcontinent, England were held 1-1 by Bangladesh then lost 4-0 in India, their 3-0 win becomes a more amazing performance.

Yes, some will point to the fact that Sri Lanka are not the force they once were. Wily left-arm spinner Rangana Herath retired after the first Test, a match in which their captain and best batsman Dinesh Chandimal picked up an injury that ruled him out for the rest of the series.

Those things are true but, for their part, England did not have the recently retired Alastair Cook. In professional sport you can only beat the opponents that are put in front of you and the tourists did that comprehensively.

It extended their run of success to eight wins in nine Tests. During the first part of that sequence, in the 4-1 home win against India, we were asking England to show signs of improvement.

Here, we got them.

The progression of Joe Root as captain has been immense. For so long, his team has been built on the pillars of Cook, James Anderson and Stuart Broad.

Now, Cook has retired and England only ever played one of Anderson or Broad in Sri Lanka. In their absence, Root was in regular conversation with vice-captain Jos Buttler, talismanic all-rounder Ben Stokes or new wicketkeeper Ben Foakes. It felt like the skipper was now leaning on his peers.

Conversely, it is a major development if the team are totally investing in the way that Root wants them to play, even if that is different to the way that things have been done in the past.

England's win has been a real group effort, with a number of individuals having fine tours.

Foakes emerged, from not being in the original squad to being named man of the series. Stokes was committed throughout and Jack Leach bowled well enough to take himself past Adil Rashid as the number two spinner behind Moeen Ali.

Buttler further vindicated the decision to recall him at the start of the home summer and Jonny Bairstow grasped the opportunity to bat at number three with a century in the third Test that will see him resume the role in the first Test against West Indies in January.

Yes, some questions remain, mainly over the openers, but coach Trevor Bayliss told me that both Keaton Jennings and Rory Burns had done enough to have more chances in the Caribbean.

For Burns, who was on his first tour, it was very hard to make a judgement, because he barely faced a delivery over 70mph. He may come up against more spin against the Windies, but, after that and if he gets that far, he will be judged on how he deals with Australia's fearsome pacemen. The Surrey man looks to have the temperament for the challenge.

Keaton Jennings made a very good hundred in the first Test and was superb fielding at short leg, but he still looks creaky outside the off stump when facing pace bowling.

Both men have a lot to play for in the Caribbean.

That trip to the West Indies starts a huge year for England in all formats. In fact, it's probably safe to say that 2019 will bring the biggest summer of cricket ever seen in the UK. It is one that I am guardedly optimistic about.

The World Cup, which starts on 30 May, is there to be won for hosts England, who are ranked the best one-day side in the world.

In an era where we try to play down expectations, I find it fascinating that Bayliss is reminding his team that they are favourites in order for them to get used to the idea.

As for the Ashes, even though Australia have not won in England since 2001, they will present a stiff challenge if they arrive fully fit in August and with their strongest personnel restored.

Can England do a historic double? We'll wait and see, but they certainly won't want for character and resilience.