England went to Australia with something approaching a plan. Alastair Cook was joined at the top of the order by Mark Stoneman - the 12th opener to try and fill Andrew Strauss' shoes - with a stylist at No. 3 in James Vince. Although that plan was quickly shown to be inadequate for regaining the Ashes, and Vince was then dropped in Auckland (where England were blown away for 58), they had a final outing in the Christchurch Test that concluded a lengthy tour of the antipodes. Vince made 76 in the second innings and finished with an average of 30.54 for the winter; England haven't picked him in a Test since.
After much badgering on the subject, Joe Root opted to once again move back up a spot. Stoneman only lasted one more Test, bowled in each innings against Pakistan at Lord's, which prompted England to go back Keaton Jennings - last seen being tortured on or around off stump by Vernon Philander and co in the 2017 summer. Cook and Jennings did not really combine to any greater effect second time around, and Root's returns tailed off after making 80 against India at Edgbaston - still, by recent standards, this was a period of stability, the top three unchanged for almost five Tests. And then…
Having been dropped in New Zealand at the end of a difficult winter (see above), Moeen Ali returned to the Test XI against India in Southampton. He made 40 at No. 7 and took 5 for 63 - so far so normal - but then appeared at the fall of the first wicket in England's second innings, apparently at his own request. Root was only too happy to switch back to No. 4, but although Moeen made a half-century in the final Test at The Oval - where Cook rubberstamped his retirement with scores of 71 and 147 - he wasn't long for the top order.
On tour without Cook anchoring the batting for the first time since 2005-06, England stuck with Jennings alongside the debutant Rory Burns. Jennings repaid some of the faith with an unbeaten 146 in Galle, were Moeen's stint at No. 3 ended; for the Pallekele Test, Ben Stokes was asked to have a go. "Ben's game is in good shape and he is more than capable of batting at No. 3," Root said. "We are fortunate that many in the side could bat in that position." Many would have to. In the second innings, Jack Leach's deployment at nightwatchman meant Stokes shunting down to five, below Root, and then another solution entirely presented itself in Colombo.
Jonny Bairstow was understandably a little peeved at how things developed in Sri Lanka. An ankle injury saw Ben Foakes take the gloves, winning Man of the Match on debut, and Bairstow found his only route back in was to bat at No. 3 in Colombo. The pumped-up celebrations of his hundred - the first for England from that spot in the order since 2016 - told a story, but Bairstow's tenure would also be short. He made a half-century in defeat in Antigua a couple of months later, before reclaiming the gloves and heading back to the middle-order at Foakes' expense.
England's fumbling for a solution saw them drop Jennings after the first Test in the West Indies, handing a debut to Joe Denly (who hadn't opened in first-class cricket since 2015). Denly was then moved down to replace Bairstow, while the woefully out-of-form Jennings was recalled - making scores of 8 and 23 - for the victory in St Lucia. Almost six month later, on the back of World Cup success, Jason Roy finally got the call, partnering Burns against Ireland at Lord's, with Denly back at No. 3. Then Leach showed up everyone by making 92, Roy shone at No. 3… and when the bottle stopped spinning it was pointing at Root again.
While Burns locked down his spot with 133 at Edgbaston, chaos reigned at the far end: Roy made 57 runs in six innings as an opener, and was shunted down to No. 4 for Old Trafford, with Denly making the jump back to the top and Root staying put (other than one innings back at No. 4 while Craig Overton shifted up as nightwatchman). But with the first New Zealand Test looming, Root decided No. 4 "suits my game a little bit more", so an arrow has been drawn next to his name with another one - Dom Sibley - scrawled in at the top. All that meant England fielded their most inexperienced top three at Mount Maunganui since the Ireland game, with just 20 caps between them: what could possibly go wrong?
Afflicted by a sickness bug in Centurion, and 1-0 down arriving in Cape Town, England were hoping to restart their tour on a more positive footing. Instead, it was Burns' stumble during a game of warm-up football that forced another reshuffle at the top. With ankle ligament damage ruling him out for the rest of the series, Kent opener Zak Crawley was catapulted into the side (having made his debut at No. 6 in New Zealand a few weeks earlier) - meaning England's opening pair went into the game at Newlands with just four caps between them. The last time they had fewer was 1963. It was also just the second time an England opening partnership had comprised two right-handers since 2002, the other occasion being Lord's 2016 when Alastair Cook came in down the order due to injury.
Alan Gardner is a deputy editor at ESPNcricinfo. @alanroderick