At the very back of a book I wrote recently, titled Raw, I offered a chapter: "How to bat six hours in a Test". It was my take on a how to become a century-maker for young aspiring batsmen. Since then, after watching a test or ten, I have been reminded again of how to do it, to make crucial runs when vitally needed, and how not to. The Ashes marathon has provided a thesis on what is, to batsmen, a very important subject.

Test cricket has forever been a game where it's the bowlers who win the matches. It takes 20 wickets, as we all know, to win. No one ever knows how many runs it takes, just that it takes crucial runs to see your side in front when the last ball is bowled. The best bowlers win Tests; batsmen need to keep the game alive, to allow their bowlers time to make their move.

What are crucial runs and why is reaching three figures in particular so important? In essence, crucial runs are those made when the bowlers are dominating, most likely due to pitch conditions. When the going is tough, either at the start with new ball challenges or overall as wickets are falling with regularity, if runs can be eked out, hard earned and against the tide, then they become the difference.

As the back-to-back Ashes series decelerate to closure, it is worth assessing the crucial run-makers, the century-makers, and the century fakers - those who pretended and failed. Firstly, some stats to give a sense of this story. There have been 20 hundreds scored in ten Tests: 14 to Australia, (ten at home) and six to England (five at home). Of the victories secured, Australia scored ten hundreds in five wins, England four in three wins, leaving four hundreds scored in the draws at The Oval and Old Trafford and two scored in losing causes - Chris Rogers and Ben Stokes in Durham and Perth respectively.

That is the stats out of the way. What is interesting to evaluate is the why and why not. When Ian Bell went on his three-ton spree on sporting pitches in the first, second and fourth Tests in England, he set up crucial victories. He was the difference. In the third and fifth Tests, Bell wasn't required to score crucial runs as the pitches were friendlier, and two draws resulted. After that, in Australia, as his runs dried up completely, so too did England.

Throughout both series, England's senior men, Alastair Cook, Jonathan Trott, Kevin Pietersen and Matt Prior, have not been factors of any note, never able to score those crucial runs. Therefore England, without Bell scoring a hundred, have been utterly ineffective. Nothing came from their senior leadership group, excluding Bell. Nothing over six months. Why? There are two reasons, I believe.

Firstly, burn out. After a dominant-but-exhausting five years on the road with all four - Cook, Trott, Pietersen, Prior - playing a crucial leading role, they have hit the wall. Secondly, natural leadership. Mainly, this group prospered under Andrew Strauss' captaincy, with the series win in India being the exception when Cook led the way.

In my opinion, there are no quality captains left in this England team. When left to focus selfishly on their own game, they are world-class batsmen. Without a natural skipper to inspire them, they become rudderless. When in charge they can't make the crucial step up and do both roles.

On Australia's side, the key to their revival, first at the Gabba, was Brad Haddin and Michael Clarke, vice-captain and captain respectively. From their tenaciously strong leadership, their less experienced team-mates followed a firm command. Leadership ruled, crucially. Why?

In Perth, Smith and Haddin showed that batting in partnership over two sessions is the cornerstone to a well-earned win

A year earlier, Haddin had an enforced break that allowed him to refresh while Matthew Wade stepped in. Clarke is simply in the prime of his life and leadership drives him fiercely. He has lifted his intensity about what was truly needed to restore the team's credentials, as he sought valuable advice from former Australia captains and mentors. Australia's rise has paralleled Clarke's step up, in all he does.

Haddin's 94 in 261 minutes at Brisbane was as good as a century. It set the scene for his form and leadership as it did for the rest of his team. Twice David Warner capitalised aggressively and brilliantly on tired bowling in the second innings but it was Clarke who always held the key. His counterattack in the second innings at Brisbane, after an ugly miscue in the first dig, was the series definer. His was a crucial hand.

It was Haddin and Clarke who reopened the can of worms for England in Adelaide. After the first day left the match on edge and in the balance, Clarke and Haddin stamped their mark emphatically, with a 200 run partnership blitz over two sessions of high quality.

At 2-0 up, Australia increased the ante. This time crucial runs came from one of their rising stars; Steven Smith became the next genuine century-maker. His first hundred at The Oval gave him a taste; in Perth he played a Clarke-like innings. Although interestingly, traces of his captain's style and functionality were shown. Smith's 111 at the WACA was a ripper. Along with Haddin (55 in 152 minutes) again, this mighty fit pair showed that batting in partnership over two sessions is the cornerstone to a well-earned win.

Melbourne came and went as England capitulated tamely, burnt out and burnt at the stake. It was as if everyone had forgotten about the art of crucial run-scoring and century-making. Bell was reduced to a first-ball waft. Cook and Pietersen pretended and succumbed. Trott, Prior and Graeme Swann were nowhere to be seen, three critical factors to England's previous success reduced to dust. No one could muster up the courage of batting two sessions, let alone build a partnership to counter the Australian force with the ball and in the field. Oh, and Haddin (65 in 143 minutes) made crucial runs again.

Finally to Sydney, and to Smith again. His appetite whetted after Perth, he produced an even better first-innings ton. Encore, it was Haddin who set the scene in tandem with his fellow New South Welshman. In 20 overs they scored 20 boundaries, the partnership a fast and bruising 128, almost identical to the one in Perth. When Haddin went for 75, Smith guided the tail astutely and in doing so gave his hometown crowd a rousing moment as he brought up his third Ashes century with a mighty six.

Smith has learnt directly from Clarke. Fresh and hungry to show his mettle to captain and country, he epitomised the qualities needed to be a crucial run-maker, a true century-maker: belief, energy, fierce focus, and following a high-quality mentor.

Haddin and Clarke, and a new leader for the future, Smith, not only stole the show with fresh vigour and energy, they showed how to make important runs and allow their fine bowlers to pounce. A mention, too, for Rogers, a resilient journeyman, relishing the chance to blossom late in his career. His two centuries in Australia came via high-quality batsmanship; a man knowing his limitations, relying on simple means and a hardened mental approach, playing for his life. Over the two series, Rogers made three hundreds (to join Bell, Clarke and Smith) and he finished the highest run-scorer (with 830) on either side during the whole campaign.

Australia, with fine leadership, proved to be the movers and shakers, and they had batsmen to score crucial runs and set each game up. Their superbly balanced bowling attack captured all 100 wickets in the five Tests in Australia, the first time this has ever happened anywhere - proving, ultimately, that the best bowlers win matches.

Martin Crowe, one of the leading batsmen of the late '80s, played 77 Tests for New Zealand