Joe Root looks dejected after being caught out by Australia's Peter Siddle in the first Ashes Test. Photo: Andrew Boyers/Reuters

Joe Root punched the rail on the way back to the pavilion. It had been a good innings, but not great. Valuable, but not priceless. Important, but not match-defining. It could, in other words, have been more.

The best batsmen in the world — and Root is certainly among them — are always on the lookout for more.

In the circumstances, 57 runs for England’s first wicket down, in a partnership worth 132 was not to be sniffed at. Root did exactly what was required of him in that position. When England’s opening pair were separated at 22 — coincidentally the average partnership total for England’s opening batsmen against Australia across the past four Ashes series — it was Root’s mission to steady the ship with experience, cool leadership and common sense. And he did that. By the time Root was out England had more than half of Australia’s first innings total and were in a position to contemplate applying intense second-innings pressure.

This hasn’t always been an easy position for England either. Going into the second innings against Ireland last week, England’s second-wicket pair had made century partnerships twice in 69 innings. Root’s promotion was intended to solve that and, in many ways, it did. He batted diligently, he batted responsibly, he batted dutifully. His first 11 runs came from 60 balls, and his half-century took 110. Everything about Root’s innings was what England hoped to get from his tweaked role. So why the frustration?

Root knows who he is. He knows why he is England’s captain, he knows his place and his importance to the team. And he knows who he is measured against. Players who, in his position, would be equally underwhelmed with 57: Virat Kohli, Kane Williamson and, most importantly, Steve Smith. The previous day Root looked on as Smith steered Australia from the brink of disaster to modest respectability. He had pushed on to 144. Had he made 57, knowing what we know now, this Test would have been close to over.

So that is the yardstick for Root. Conversion rate, 50s to 100s. The biggest scores made by the best batsmen, interventions that win matches, not just lend a helping hand. Root punched the rail because he got in, then got out; because he knows that had he matched Smith’s total from Thursday this Test would have been halfway home by now. England would be ahead of Australia’s first innings total with nine wickets in hand. He might not even have been required to bat a second time at Edgbaston, had all gone well.

The master batsman, Sir Don Bradman, had a phenomenal conversion rate. He got to 50 on 42 occasions in his career, and on 29 of them pushed on to make a century. Michael Clarke and Matthew Hayden were also quite exceptional. Hayden made 30 centuries on the 59 occasions he reached 50, Clarke converted 28 times out of 55. To hover around the 50 per cent mark in the modern game is no small feat. That is what places Smith among the giants of the game. His innings on Thursday was the 24th Test century of his career, and on 24 occasions he has been out between 50 and 99. Kohli’s numbers are even more spectacular: 45 half centuries, converted to 25 centuries.

Root, for all his talent is nowhere near this ratio. He has reached 50 on 58 occasions and 100 on 16, a conversion rate of little more than one quarter. And in most series, a batsman scoring between 50 and 99 will stand out, as Root often does.

The Ashes, however, demands more. It brings the best from the best and statement performances resonate. It is close to impossible to imagine Rory Burns now making way for a rival opener in this series, having made a century on his Ashes debut. Whatever doubts remain about his technique, whatever alternate concepts may have been under consideration, Burns displayed enormous character to thrive under pressure, carrying his bat through the entire second day. The Ashes brought the absolute best from him.

The debate around dropping Jason Roy down the order may linger, but Burns’ position is safe. If England take a series lead, his performance will be synonymous with this Test. That is what Root wanted for himself.

Not because of ego, but to lead from the front, as he explained on the eve of the Ashes. Everyone knows he prefers to bat at four. He has moved up the order, selflessly, to remove some of the pressure from a callow top three. It was the act of a good captain, and a good man. So his mask didn’t slip because he wanted the glory. He just wanted to be of more use. Perhaps it is just as well then that he was saved early on by another of those curious anomalies that seem increasingly to affect modern cricket: the unmovable bails.

England’s score was 53 for one, Root on just nine, when he was given out, caught behind, off the bowling of James Pattinson. The finger had barely been raised when he reviewed, a sure sign justice had not been done.

The review immediately confirmed no contact with the bat as the ball passed — but there was a plainly discernible noise a split second later. Pattinson’s delivery had glanced the stumps — not struck, but certainly with enough force to be noticed and heard — the bails had skipped in their grooves and then resettled. What is going on with the modern equipment? Did this used to happen in what might be termed the good old days, and we missed it? Television isn’t such a very new invention. Surely someone would have picked up on it?

The bails refused to drop, stumps hit, on five occasions in this summer’s World Cup — all in early group games, and then not again. The ICC insisted no modifications had been made, or were required, yet the evidence sparked suspicion. And this is the first match in the ICC World Test Championships, too. Let’s see if it happens again.

Either way, Root was a lucky chap. If 57 had him taking it out on the furniture, who knows what repairs would have been required had he fallen for single figures?

Still, with Burns in and Ben Stokes jogging along nicely, England remain in a position of strength. And it is healthier for England’s captain to take heart from that than personal statistics. To bat conservatively, to limit his game in the search for elusive conversion numbers, is hardly going to help England’s cause. And 57 in an Ashes Test — in any Test, really — is no calamity.

It is not the last word, however. There is perhaps a little too much conversation left in this game for Root’s liking.

Daily Mail