But the struggles of Keaton Jennings - Cook's 11th partner in five years - detract attention from the issues in the middle order. Since Bayliss took charge in the summer of 2015, England have chosen 18 players to bat in their top five, more than any other Test nation. Cook and Root, the two constants in that period, average a combined 47.27. Between them, the rest have managed an average of 24.83. Test cricket provides a forensic examination of a batsman's technique. Adam Lyth, James Vince, Ben Duckett, Gary Ballance and Alex Hales have had their flaws exposed.
It can also be argued that leading candidates in county cricket now have to do less to stand out from the crowd. All of Jennings, Tom Westley and Dawid Malan - current incumbents of Test spots - have first-class averages under 38. Why is the domestic game failing to produce enough batsmen capable of succeeding at Test level? "We have had so many players that have come in and failed because of poor technique," said former England batsman Geoffrey Boycott.