Well, last year against India England made it to 400 in a test match innings. As far as I've been able to check, that's the only time in the last two years, in test match competition. Now maybe I'm way out of date, but in my book, 300 is just an o.k. score in test cricket. It's not exceptional, it's just o.k. 400 is good, 500 is impregnable. You're supposed to build an innings, patiently, even cussedly. It's not 50 overs, you've got time (although I do find myself wondering what effect the white ball game is having on the red ball game, as far as batsmen's patience and concentration over a sustained period is concerned. Some can do it, mind…)
It is high time England aimed at knocking up 400 over the next two days. It's not rocket science. It's cricket at top level. If they are top level batsmen.