If there is one thing that defines the town of Diss it is the mysterious body of water known as the Mere at its heart.

Diss takes its name for this body of water – Dic or Disce is the Saxon word for ‘ditch of standing water’ – and describes one of the deepest natural inland lakes in the country.

For many years, there was a persistent rumour: that the deep lakelet was, in fact, a flooded natural volcano crater, a remnant of a fiery past.

Like similar crater lakes, the Mere is almost circular but Norfolk has no records of volcanic activity and the landscape suggests there was none in the county.

Another suggestion was that the depression in which water pools was formed by “a historic plasma discharge event”. Details of which are not forthcoming.

Further tales claim the hole was created by a huge meteor which fell from the sky and found its home in south Norfolk, before burning away and leaving a hole which was later filled with rain water.

In the EDP of June 16, 1896, a somewhat unsavoury tale was told of the Mere.

“All sorts of stories have been told about this lakelet, as that it could not be fathomed, and that it was the crater of a volcano,” it read.

“The real depth is said to be from about 17 to nearly 20 feet, and its muddy bottom, formerly the receptacle of all the town sewerage, swarms with eels.

“In an old volume of the Gentleman's Magazine it is stated that in Diss there is a fish, found nowhere else in England, called by the inhabitants ‘chasers’, probably the same as are called in Germany China carp.

“We were assured that there are fish in the Mere still called chasers by the inhabitants, but closely resembling pike. This cannot be a mere myth. Blomefield said that the Mere ‘purges itself’ once a year, and that it then stinks exceedingly, and the fish rise in great numbers.”

The UK has not had active volanoes for around 55 million years because the country is not particularly close to the edges of the tectonic plates that make up the Earth.

It is at these boundaries where volcanoes tend to form.

The geological history of the UK shows a rich variety of landscapes and formerly active regions of volcanism across the Lake District, Snowdonia, Northern Ireland, southern Scotland, western Scotland and Dartmoor.

Eastern Daily Press: It used to be said that Diss Mere ‘purges itself’ once a year.It used to be said that Diss Mere ‘purges itself’ once a year. (Image: Archant Norfolk Photographic © 2015)

In the Cambridgeshire village of Warboys, studies by the British Geological Survey discovered the core of an ancient volcano from 300 million years ago – this is the closest to Norfolk that volcano activity has been found.

Weird Norfolk grudgingly accepts that the most likely explanation for the formation of Diss Mere is that it is a natural basin caused by the collapse of the chalk bedrock at the end of the Ice Age.

In the harsh winters of the 19th century ice carnivals would be held and Diss residents would wear fancy dress and carry Chinese lanterns as they walked on the ice.

On one famous occasion in 1827, a cricket match was played on the Mere.

Beneath the deep water lies an estimated 23 metres of mud, and in this mud the eel population mentioned above were said to, during Victorian times, willingingly end their own lives by jumping out of the Mere due to the noxious waters.

The Mere was, at this time, polluted by the hatters and dyers who dumped their mercury-rich waste into the water which, when added to the town’s sewage, made for a potent brew that seemingly made death preferable to the eels.

In addition to legends that link it to a long-since dormant volcano, the six-acre Mere is home to more than 50,000 fish, once boasted a 122lb, 8ft long catfish and was where an acrylic cast of a human head was dredged up.

The huge catfish or ‘Monster of the Mere’ was caught in August 2020 and was removed by the Environment Agency, taken to an undisclosed site and released.

Whether Diss’ eels are still undergoing night-meres is unknown.