The Royal Navy is to conduct a major anti-submarine exercise off the coast of Cornwall and in the Western Approaches in June.

Not since the days of the Cold War have so many Royal Navy helicopters been sent to sea on an aircraft carrier for the purpose of hunting submarines as on Exercise Deep Blue in the Western Approaches.

Nine Merlins from RNAS Culdrose in Helston will join HMS Illustrious to practise skills which were once the mainstay of the Royal Navy’s aircraft carrier operations at the height of the tensions with the Soviet Union.

It will be the first time the latest version of the Merlin – the Mk2 – has been tested en masse.

After more than a decade on the front line, the Merlin fleet, based at Culdrose, is in the midst of a £750 million revamp which will help to keep them at the forefront of naval warfare until the end of the 2020s.

It will spearhead Deep Blue, with eight new Mk2s due to join the Portsmouth-based carrier, plus one Mk1 – the largest concentration of submarine-hunting helicopters in recent memory, and the largest ever concentration of Merlins at sea.

“Nine Merlins on one carrier is a sight no-one has seen – and one no-one involved will ever forget,” said Commander Ben Franklin, Commander of the Royal Navy’s Maritime Merlin Force.

“We’re looking forward to it big time. The younger guys especially. They’ve heard all the stories about what we did back in the days of the Cold War because, if the balloon goes up, this is what we do.”

A couple of next-generation Merlins from 820 NAS have just returned from Dynamic Mongoose, a NATO anti-submarine exercise off Norway, where they clocked up 60 hours in the skies over the North Sea.

Cdr Franklin said: “Dynamic Mongoose was ‘toe in the water’. Deep Blue is on a far grander scale.”

After more than a week training around the UK by day and night, Illustrious and her helicopters will move out into the expanse of the Atlantic for Deep Blue itself, which reaches its climax in mid to late June.