You wouldn't normally think that Boris Johnson and David Warner had much in common. But, as Warner trudged off the pitch at Old Trafford on Wednesday, he could be forgiven for identifying with Johnson and ruing how hard it can be to leave something. Even if you really want to do so.

For the second time this series, Warner had been dismissed trying to leave but failing. Perhaps more revealingly, it was the fifth time in the series - so the fifth time in seven innings (and 87 balls) - he had fallen to Stuart Broad. This time it took Broad only two balls to get him.

That marks quite a turnaround in the head-to-head record between the two players. Going into this series, Broad had taken Warner's wicket only five times in total - that's five times in 29 innings (and 527 balls) - with each wicket costing him 64.80 runs. In this series, Warner's wicket is costing him just 6.40 runs each time.

Key to this change in the balance of power has been Broad's decision to aim more at Warner's stumps. He has, in the past, looked to find the outside edge of Warner's bat. And while he has alternated between bowling round and over the wicket to him, in this series Broad has operated exclusively round the wicket to Warner, angling the ball and testing both edges of the bat. Broad had never previously dismissed Warner while bowling round the wicket.

At the same time, Broad is also bowling fuller than ever. Prompted by the coach and analyst at Nottinghamshire, Broad realised his leave percentage - the number of deliveries which batsmen were able to leave against him - was too high and resolved to bowl fuller more often. He has never exceeded the percentage of full deliveries he has bowled this series in any previous home summer - 37 percent - and, perhaps tellingly, he has never enjoyed a better average (currently 20.39) or strike rate (38.10), either. He reckons he is bowling better - and quicker - than for three or four years. He may be something of an old dog, in cricket terms, but he has shown he has the hunger to learn new tricks.

"Up until this series, Warner has had the better of me, really," Broad admitted ahead of this game. "I'd always focussed on his outside edge thinking running the ball across him would bring in the slips.

"I had a change of mindset in this series a little bit to try and bring the stumps into play more to him. I'm looking to nip it back onto off-stump. Then, if it holds its line, it brings the outside edge into play and that actually limits the scoring options slightly."

There are other factors at play. Conditions in England at present - the pitches, the weather and the balls - have all combined to make life desperately tough for opening batsmen of both sides. Over the last two seasons, opening batsmen in Tests in England dare averaging a meagre 22 - almost half the figure it was between 2000 and 2009 when it was 40 - with the England bowlers mastering the wobble-seam delivery that gives the batsmen few of the clues of conventional swing or seam bowling. You have to go back to 1932 to find a summer in which opening batsmen have averaged lower.

"I don't want to take too much credit for out-thinking him or anything," Broad admitted. "The fact is it's been a really good time to bowl with that new ball. And the pitches have been in our favour, too."

All this has created something of a perfect storm for Warner. Already standing out of his ground in an attempt to negate the lateral movement of the ball, Warner has given himself less time to judge which way the ball will move and, as a consequence, is increasingly unsure which balls to leave or play. The crisp, certain movements that have typified his career have been replaced by hesitancy and timidity. Here, where he lasted just two balls, he looked confused and muddled.

That is borne out by the manner of Warner's dismissals to Broad. Three times Warner has been dismissed by the ball angled in to him - twice leg before; once bowled - while the other two occasions have seen him caught in two minds; knowing, on one hand, that he should be leaving the balls outside off stump but unsure, on the other, if they were the ones jagging back into him. The result has been two tentative leaves, with the ball brushing the edge of the bat as the batsman half-heartedly tried to withdraw it.

The emergence of Marnus Labuschagne and the sustained excellence of Steve Smith have allowed Australia to cope with Warner's decline. But in one key battle, England clearly have the edge.