More mental fatigue than anything else, at this level they all can play cricket. All was needed was block for 3 sessions and it was a drawn match! Kohli and co didn't let up on pressure and the difference ultimately came down to leadership - yes, Kohli!
I think Cook's done. It time for a New England Test captain. Root is not the man. He and Cook should focus on runs and records. My pick would be Benji - a fiery character when given responsibility will shine like Kohli. Test cricket has changed in last few years, drawn matches are a rarity and teams need fiery, aggressive captains to fight and win.
Also, England should separate the Test crew from ODI and T-20. All-rounders like Benji are an exception. Test should be treated as a different discipline all together. Haseeb in Test team. Duckett ODI. Bairstow Test. Billings, Butler ODI/T-20. Broad and Anderson have seen their prime and it is time to start experimenting with substitutes. ECB system has enough talent to fill the spots and then develop and groom the players.