A stretch of walkway in Sheringham was closed to the public by North Norfolk District Council on January 14 after the void was first discovered.

Initial investigations described the hole on the eastern end of the beach as large enough to "accommodate a Transit van" and work began to fill it last week.

Now Brian Farrow, coastal engineer at NNDC, has taken to the camera to explain what may caused such a large sinkhole and the process of the investigation.

More than 200m³ of concrete has been poured into the void since the work started (Image: NNDC)

He said the sea wall was built around the 1920s and founded on chalk - a soluble material which the sea can cut through.

And behind it, there is sand and gravel, which are then easily washed once the water cuts through the underside of the wall.

"We drilled some small holes in the slab and dropped a half inch rod in. The rods then disappeared so we knew we had a big sinkhole," Mr Farrow said.

"We then cut 12 inch holes in so we could see much better. Surprise, surprise - we found a massive hole."

The void was previously described as 'large enough to accommodate a Transit van' (Image: NNDC)

Since the work began last week, more than 200m³ of concrete has been poured into the void.

And as the project continues, the council has advised the public to stay clear of the area and "do not cross through the safety barriers demarking the site".

The progress will be monitored over the coming weeks but it is still unclear at this stage when the work is likely to be completed, nor when the section of the promenade will be reopening to the public.

So far it is believed to be an isolated incident and there are no other ongoing investigations into similar incidents.

However, the council has said that the promenade in Sheringham is routinely monitored alongside other infrastructure around the coastline.

© Eastern Daily Press