Southsea promenade uncovered during sea defence works

The walkway is believed to be the original front edge of the old promenade going around Southsea Castle

Part of an Victorian-era seafront promenade has been uncovered during work on new sea defences on the Hampshire coast.

Workers discovered a 2m-thick (6ft) stone surface under the tarmac near Southsea Castle.

It is believed to be the original front edge of the old promenade, which was constructed in 1848 and built on top of the castle's defensive tunnels.

Wessex Archaeology said it was "an important part of the local story".

Contractors, working on initial studies for a £131m project to build new sea defences were boring holes in the current footpath to investigate the depth to the tunnels below.

Contractors found an old promenade beneath the current tarmac path

They had expected to find gravelly material, but instead found solid stone.

Richard Samphie of Royal Haskoning DHV said the find was a "huge surprise".

"It's a huge leap forward in our understanding of Southsea's history as, until now, we didn't know what was between the footpath around the castle and the roof of the tunnel," he said.

The tunnels beneath the promenade form part of an early 19th Century redesign of Southsea Castle that allowed defenders to fire into the moat at attackers.

The path around the outside of the castle was in use from the middle of the century when it was still an active military base.

Naomi Brennan, senior heritage consultant at Wessex Archaeology, said it had been assumed the old walkway had been lost when the modern surface was put in.

"It's an important part of the local story. The discovery highlights the change in Southsea from a purely military site to a fashionable holiday resort during the 19th Century," she said.

The sea defence scheme involves building walls, raising land and widening beaches along a 4.5km (2.8 mile) stretch of coastline.

The path sits above the castle's underground tunnels