Carole Middleton was on a river trip with a group of keen snappers.

She pointed her camera at a tall chimney and streetlight in the evening gloom.

But when reviewing her shots later she was shocked to see the mystery object apparently hovering above.

The mysterious saucer-shaped green light appeared above an old water pumping station in Cambridge – now home to the city’s Museum of Technology.

After Carole’s image was shared on social media people began to speculate on what the object was.

One joked that the chimney is “a well-known intergalactic beacon for UFOs”.