Really? Will LHR be full to capacity from day 1 whatever the capacity?
Is it really better to operate the system at 98% rather than 95%? That must depend on the shape of the delay curves but in principle say 20 mins knocked off the journey times could be worth a lot to the business traffic, and improved reliability could be worth a lot to the connecting traffic. Obviously that is not solely a function of runway capacity.
I think the case for R3 will be partly a case based on operating more efficiently, not purely a capacity case.