Work to refurbish a lock on the River Medway will take an extra three months to complete after a major structural fault was discovered.

The Environment Agency (EA) is carrying out the first major maintenance work on East Farleigh Lock in more than 100 years as part of a £3 million scheme to improve the waterway system for wildlife and mariners.

But contractors working for the government organisation have discovered a major structural problem with large section of wall behind the left-hand lock gate. This will have to be demolished and rebuilt.

Philip Munslow, waterways operations manager said: “This unforeseen work will take a further 12 weeks to complete. It is therefore anticipated that the lock will remain closed until the end of June 2017. We apologise for the inconvenience."

Because of the construction, the portage route around the railway side of the lock could also be closed on weekdays and the nearby footpath will also remain shut.

The works, which began in September are part of a scheme to improve 10 locks along the Medway, the majority of which will be given fish passes to allow the river's population of pike, perch, roach and common bream to navigate the span.

East Farleigh is the second lock boaters arrive at if visiting from the tidal river and heading upstream.

While the lock is closed access is cut off for boaters who in April head up to Medway in droves for Rochester's Sweeps Festival.