England v New Zealand: Joe Root finds his smile with Lord's hundred - Agnew

As a captain, Joe Root had a torrid winter.

England's beatings in Australia, then the loss in Grenada that sealed a 1-0 series defeat by West Indies left a deep and damaging mark.

It's no surprise to hear Root speak about the effect the job had on him. It weighed so heavily on his shoulders - the England captaincy should come with a health warning.

Even then, it is a big thing to give up. Root stood down in April, but is probably still hurting about what happened. You don't just resign and forget about it.

And yet, in his first Test back in the ranks, Root was able to make a fabulous match-winning hundred against New Zealand at Lord's. It was up there with the best I have ever seen him play.

On top of that, he reached 10,000 Test runs - only the second Englishman to do so - with his wife, children and parents there to see it.

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Root was in tears as he left the field and that emotion would have triggered those who have worked closely with him. It certainly did to me.

It wasn't uncommon that I interviewed Root three times a week during his captaincy. Some of them, after particularly bad defeats, were horrible experiences.

At Lord's, his impish smile returned and it was lovely to see.

I hadn't actually spoken to him, since he gave up the captaincy, until before the start of this Test. At that point I simply said to him that he should "make bowlers cry" this summer. I had no idea it would be Root and the rest of us wiping our eyes.

It is my belief Root is one of the very best batsman England have produced since World War II. There are some - Colin Cowdrey, Peter May and Tom Graveney - that I only saw on television. Others, like Geoffrey Boycott and David Gower, I shared a field with.

What makes Root so good is his technical expertise - he has hardly got a weakness. The right-hander is so busy at the crease, he gets the scoreboard rattling along. It is the rhythm and tempo of batting that Root commands so brilliantly.

Now, freed of the captaincy and playing under Ben Stokes, Root can focus on scoring bags and bags of runs. Every record you can think of is up for grabs and within his reach.

That is certainly what Stokes will want, not only because he will like his great mate to succeed, but because the more runs Root scores, the better it will be for Stokes' England.

It was actually a nice line from Root when he said Stokes had produced so many performances when he was captain, it was now his turn to start repaying the favour.

Root and Stokes have known each other since they were very young, long before either of them played for England. As they have made their way in the game, they have been together for pretty much every major moment involving the England team across the last decade.

There are lots of similarities between the two of them, with one being the deep care they have for their team-mates. They are always looking out for others, making sure they are OK.

Stokes, for example, was celebrating his 31st birthday on Saturday, the third evening of the Test.

His wife was in London from the north east and his mum and brother had travelled all the way from New Zealand to see his first Test as captain.

When they all went out for dinner, Stokes made sure Matthew Potts went along. Not just because they are mates from Durham, but to ensure the bowler, on his debut, wasn't sitting brooding in his hotel room about the prospect of having to win the Test for England with the bat on Sunday morning.

As it turned out, Potts wasn't required because Root and Ben Foakes took England to what turned out to be a fairly emphatic five-wicket win.

It ensured a successful start for new captain Stokes and coach Brendon McCullum. It should have a positive impact on a dressing room that had only tasted victory once in the previous 17 matches.

If you were being picky, you could say that the new era was very much like the old era, with England relying largely on the same players.

Potts had an excellent debut, but it was Root, Stokes, James Anderson and Stuart Broad upon whom England depended.

On the other hand, it can be argued every England player will head up the M1 to the second Test at Trent Bridge justifiably thinking they made a contribution to the win.

Zak Crawley and Alex Lees shared a solid opening stand in the first innings. Ollie Pope produced a direct-hit run out and Jonny Bairstow took some fantastic slip catches. Matt Parkinson claimed his maiden Test wicket and Foakes played his part in a match-winning stand with Root.

There were times when England should have won comfortably - and others when they should have lost.

When it really mattered, they stood up. They had to bowl out New Zealand on the third morning and they did. They had to dig in to complete a stiff run-chase, and they did.

Clearly, one win does not change too much and we all know England have a long way to go.

Still, winning this Test is a lot better than losing it and the good feeling should stretch to all parts of English cricket, including the supporters.

Bring on Trent Bridge.

Jonathan Agnew was talking to BBC Sport's chief cricket writer Stephan Shemilt