A murder trial at the Old Bailey was temporarily suspended, because of a rodent running around the dock.
The court assigned the most formidable usher to deal with the issue, while one defendant in the trial knelt on his chair to prevent the animal – believed to be a mouse – from climbing up his trousers.
The staff member attempted to grab the intruder and catch it with an empty water jug.
However, it darted away into a neighbouring courtroom.
The jury were temporarily removed from the room while the situation was dealt with.
Sources told the PA news agency they looked unimpressed by the interruption.
Last year, a man in the south-west of England was faced with a mystery when tools kept moving in his shed.
Stephen McKears from Gloucestershire was puzzled after items he left on his workbench kept being put away overnight.
First he blamed himself going mad, then he thought a poltergeist may be at work.
It later turned out to be a houseproud mouse.