Police were called to the home of artist Sam Taylor-Johnson and actor husband Aaron after a passer-by spotted a machine gun on a desk inside the house.
The gun, a deactivated M16 assault rifle, had been given to the film-maker and photographer as part of an art project.
A spokesperson from the Metropolitan Police confirmed firearms officers were called after the gun was spotted through a window of their north London home shortly before midnight.
We can confirm that early this morning police were called to the London home of Mr and Mrs Taylor-Johnson following a report of a firearm on the premises by a concerned passer-by. The family were not present in the property at the time but the police gained entry via a key holder.
The firearm was located in Sam Taylor-Johnson's basement studio and has been confirmed as a certified and fully decommissioned M16 assault rifle that was provided to Mrs Taylor-Johnson by the international charity Peace One Day as part of an art project entitled 'Peace One Day M16'.
The project, curated by Jake Chapman, consists of new works by some of the most celebrated names in contemporary art all of whom are transforming fully decommissioned M16 assault rifles.
More top news
Rowan Atkinson slipped back into character for the 25th anniversary of Mr Bean and took his mini for a spin outside Buckingham Palace.
A woman believed to be in her 60s has bee killed after being hit by a lorry in Peckham High Street, police said.
Researchers from Imperial College London believe they have found a cure for motion sickness.