2 circuits at the same time...... are you kidding me??
It may be apples to oranges, but in the US, where many airports have parallel runways, this isn't uncommon. Only today, we had 2 planes doing patterns on one runway, with 2 more on the parallel runway.
I understand that LHR normally uses one runway for arrivals and the other for departures. Is that the case at most other UK airports?