A swarm of motorbikes

There are strange things that happen sometimes. Two days ago, driving back from Beaconsfield in the evening, we had to wait at an intersection for ages: there were motorbikes going across. Not easy riders but some of these Japanese types motorbikes made for speed. They were rolling like hornets, one after the other, way faster than they should on such road. The driver behind us got impatient, but there was no opening for a few minutes. Later on, another motorbike took us over and we saw yet another near home. I really wonder what it was, where they were going and why were they so many.