Anyone who flies in /out of LHR on a semi-regular basis knows that you are amazed when you DON'T have to hold (BA or not) - ATC have to juggle heavy's and lights, they also have to keep an eye on trafic needing to cross runways on the ground to & from the terminals so the whole of the airport isn't one enormous parking lot
It's not an easy job but I think they get it right most of the time TBH