Odd stat about the proportion of wickets falling in the first session being nearly half.
Before the 5 this morning, it was 9 out of 25, which is near enough 1/3 (so uniformly distributed), now it is 14 out of 30, so nearly 1/2 !
The new ball took the wickets this morning really and that is how it has been in general, so I think the correlation of sessions to wickets is misleading - it is all about the new ball and it is important that amidst any rain delays that England take their chances with it.