An ancient Egyptian statue has left staff at Manchester Museum puzzled after it started slowly rotating inside its glass case.

The 10ins (25cm) high stone statue, which dates back to 1,800 BC and was donated to the museum by a private collector in 1933, has been caught moving on time lapse video.

The phenomenon was only noted after it was moved to another display area a few months ago.

Egyptology curator Annie Garnett said various theories have been advanced ranging from vibration caused by nearby traffic to visitor footfall.

"Professor Brian Cox thinks it is due the differential friction between type of stone and the glass shelf it is on," she said.