Their tent was spotted by Environment Agency officers taking part in an exercise during the early hours of today.

Eastern Daily Press: On Patrol: The EA at Hunstanton BeachOn Patrol: The EA at Hunstanton Beach (Image: Archant)

Teams were out practising their response to high tides in and around King's Lynn.

They included fitting dam boards to defences around King's Staithe Square.

Alan Daniels, Environment Agency Operations Team Leader for Kings Lynn, said: 'Having seen the forecast for the morning's tide yesterday and despite this now coming in under the predicted level and our normal trigger level for response on the ground, we decided to take the opportunity to exercise our staff.

'The exercise went well. While most people were sleeping we opened our Kings Lynn incident room at 2.50am to oversee the activity.

'Our teams were in town by 5.50 closing all flood gates, where access was non essential, ahead of high water which was expected at 08:48.

'Our Coastal Patrol did have to wake five sleeping teenagers who were camping on the beach at Hunstanton – rather us wake them at 6am than the waves a few hours later.

'The boys were all happy to vacate, once we'd explained the situation and advised them that future camping excursions would be more successful if they had a better understanding of the local tides.'

This week's tides are known as Spring tides, which occur around the new and full moon when its gravitational pull is strongest.

If a Spring tide is accompanied by low pressure and strong north-easterly winds a surge can be created. Low pressure causes the surface of the water to bulge, making the predicted tide even hhigher.

Kings Lynn's flood defences were severely tested on December 5, when these conditions last occurred causing the East Coast Tidal Surge.

Kings Lynn experienced its highest sea levels in recent history exceeding both 1953 and 1978 levels.