It was the surveillance cameras trained on the dark corners of St Matthias church in the village of Castenray in the Netherlands that caught the creatures in the act.

The video footage is in black and white, the animals are entwined and upside down, and the events that unfold against a metal grill are more frantic than romantic.

But the recording may nonetheless prompt the rewriting of textbooks. Researchers believe the film of serotine bats is the first documented evidence of any mammal mating without intromission. In plain English, that’s having sex without penetration.