A schoolgirl captured on video a mysterious black circle hanging in the sky over Leamington Spa on Friday.

Georgina Heap, 16, was playing tennis with mum Jo when she spotted the strange sight, with the giant dark smoky ring lingering in the air for around three minutes before disappearing.

The ring has got UFO hunters excited, and officials have been stumped, but the ring is actually something known as a “vortex ring” in this case caused by firework tests at Warwick Castle.

Most vortex rings are caused by some form of explosion, such as a powerline transformer, with the rings formed by air mixed with smoke forced through a cylindrical opening. The air in the centre of the cylinder will be expelled more quickly because of drag around the edges. The air from the sides is sucked in, creating a circular motion and the vortex you see in the video, with the ring hanging in the air as long as the rotational motion of the air continues.