Essex police officers have been involved in one of their most unusual wildlife operations – to prevent as many as 40 whales from being stranded on beaches or sandbanks.

Officers from the marine unit and the helicopter were called in after the pod of pilot whales was seen entering the River Blackwater yesterday - Tuesday, November 18.

Members of the charity, British Divers Marine Life Rescue, called police and Coastguard when the whales were close to shallow water at St Lawrence Bay.

The Special Branch Marine Unit used a high speed RIB to reach the scene and with local boats managed to turn the pod back towards the open sea.

The mammals, which were believed to be following and eating shoals of herring, were later seen heading towards the shore between St Osyth and Jaywick.

Marine officers then called in a helicopter from the National Police Air Service. Also on board the aircraft was a technician from a mapping contractor who had previously served In the Royal New Zealand Air Force and had experience in marine surveillance and monitoring whales in Antarctica who was able to provide valuable information.

Pc Kevin Flinn, observer on the helicopter, said: "Our passenger was certainly an expert on using aircraft to shepherd the pod of whales. We hovered between the beach and the pod and were able to move closer to them until they turned and went back to deeper water.

"The whales were about five metres long and in very shallow water and with the tide receding. There certainly was a risk of them beaching on the sandbanks but we moved them away from danger. The marine unit boat and other vessels then took over and escorted the pod further offshore.”

At one point the helicopter descended to about 200ft to ‘flag down’ a local fishing boat that was heading straight for the whales. The officers used their Sky Shout broadcasting system to alert the crew of the boat. The vessel stopped and the skipper was asked by the marine unit to steer clear of the whales.

Pc Simon Lofting from the Special Branch Marine Unit said: "We have had small numbers of dolphins and porpoises off Essex but this is the first time so many whales have been seen. We had been out the previous day on The Thames when there were sightings off Southend and Kent, but we did not find them.

"But on Tuesday following sightings in the River Blackwater we were contacted by British Divers Marine Life Rescue and asked to assist. We had an expert from BDMLR on board our boat and he had real concerns that the whole pod could strand themselves.

"The helicopter did an amazing piece of work, not only moving the whales from shallow water but counting them accurately when the pod had split. We were told the previous day that there were 29 whales so the helicopter was a great resource in giving us accurate information.

"I would also like to thank the assistance of Inshore Fisheries and the river bailiff, between the three vessels we managed to bring the whales together when the pod split and we moved to deeper water.

"It was certainly one of our more usual operations and we all worked closely to ensure that the whales were not stranded in shallow water while chasing shoals of herrings.”

The marine unit has been involved in monitoring the whales today.