A handgun has been found in Camden lock after it was drained.
The corroded weapon was discovered this morning.
Police said the handgun was not dangerous and had no firing mechanism.
The lock was last drained around 25 years ago, in the early 1990s.
It was drained last week but the weapon was only spotted when silt and other grime was removed.
The lock, one of two that sit next to each other, was drained so the lock gates could be replaced – something that happens about once every 25 years.
There will be a silent disco there on Saturday as part of celebrations to mark the completion of the project.
Police have allowed organisers to display the gun at this weekend's events, before they take it away to examine it further.