This should be a crucial moment in the career of Harry Brook.

After the thrilling highs and frustrating lows of the past four years and 38 Tests, he stroked 91 runs from 93 balls without breaking sweat on day two of the first Test against Pakistan.

The wild swipes of previous innings, particularly during England’s Ashes defeat last winter, were gone. Not once did he come charging down the pitch.

Yes, he was dropped on one but after that he just kept his concentration and knocked bad balls for four.

He will score a million runs if he keeps batting like this. It must be the blueprint for Brook across the rest of his Test career.

Any frustration I have ever expressed towards Brook has never been personal, or because I did not rate him as a batsman.

He is a very rare talent who ranks alongside the likes of Kevin Pietersen and David Gower as the most talented I have seen play for England.

There have been times, like during his triple century against Pakistan in Multan, when I have sat and admired that talent.

But in Australia, when he got out driving Scott Boland in Perth or swinging at Mitchell Starc in Brisbane, I feared he could waste what he has worked so hard to have.

It is no surprise this version of Brook has come immediately after he was overlooked as captain.

He was seriously considered by managing director Rob Key and others at the England and Wales Cricket Board before ultimately being overlooked.

I am sure he will have asked himself why that was the case and, after incidents like the one in Wellington and some of the things he has said to the media in the past, it comes back to maturity.

Yes, Brook has shown himself an able tactician and leader of the white-ball team but at no point did I believe he was ready to be England’s Test captain.

That role is about more than purely the decisions made on the field.

It is about representing your country, and sometimes stepping up when needed to talk about difficult topics around the world. We have seen that in the episodes involving Zimbabwe and Afghanistan in the recent past.

Brook has not shown he has the maturity to do that part of the job, meaning Joe Root was the only candidate. The hierarchy had no choice.

But Root’s second stint is unlikely to last long, possibly only until the end of next year’s Ashes, and the ball is in Brook’s court to show before then that he is the best candidate next time around.

Who knows, Jacob Bethell, who is highly rated as a leader, may have overtaken him by then but there is no reason Brook cannot be Test captain when Root leaves the role, especially if he is showing maturity through batting like this.

Of course, some people will view Brook’s innings through the prism of what has come before. They may say it only adds to the frustration around why Brook could not bat more sensibly during the Ashes.

Who knows what may have happened if he did.

I get that argument – the winter was one of the biggest disappointments in recent memory in English cricket – but it is now time to look to the future, and time to put the Ashes behind us.

Lessons have been learned; you can see that by the decisions made and the people now in charge. Root and Stephen Fleming should be more astute operators.

So, with big series on the horizon after this – a winter trip to South Africa and then the Ashes next summer – it has got to the stage where we have to move on.

With that in mind, it was not just Brook’s performance that has been encouraging so far.

Though he will be annoyed to get out misjudging the length of spinner Usman Ali as Brook did, Jordan Cox batted with similar restraint and class for his 73.

Root batted as he does, holding together a more measured batting performance. It was something every England fan will be happy to see.

While two calm days have been most welcome after what we have witnessed in recent months, we do not want England to dispense with everything we saw under Brendon McCullum and Ben Stokes’ Bazball regime.

This team should retain a lot of their positivity, but do so without delving into the recklessness and inflexibility we saw before.

Ruthlessness was another thing the Bazballers were often lacking and this Test has presented Root’s England the perfect opportunity to show what they have learned.

Pakistan have picked the wrong team. They should have picked another seamer and are desperately missing some pace in their attack.

It means this is as kind an opponent England could have wished for to start their long-awaited reset.

England can now press home their advantage and go 1-0 up in this series. Brook has begun to show them the way.

Jonathan Agnew was speaking to BBC Sport’s Matthew Henry