Since they first entered service with the Royal Navy in 1998 and with the Royal Air Force in 2000 the Merlin Mk1 and HC3 helicopters have been steadily growing in operational importance.

Now, as the Royal Navy's Merlin Mk1 declares Full Operational Capability, it is clear it has become one of the world's most effective Anti-Submarine Warfare (ASW) platforms. But with the end of the Cold War, the rise of asymmetric warfare and the land-based conflicts in Iraq and Afghanistan dominating the headlines for the last few years, ASW has begun, to some, to look a little dated. A hangover from the cold war perhaps, or an unnecessary use of precious resources.

But observers taking a wider perspective will be less surprised by a recent resurgence in activity as submarines, thanks to their unparalleled ability to project power stealthily and over great distances, remain key components of armed forces world-wide. There is a growing capability in the waters of the Middle and Far East, Malaysia is expecting her first Scorpene-class to become operational in 2009, Norway has begun concept studies for submarine capability post 2020 and here in the UK work continues on the new Astute-class boats, with the first launched into the Clyde earlier this year. Looking ahead and a new class will replace the HMS Vanguard fleet of Trident submarines which are due to exit service by 2024.

Developing technology in diesel-electric propulsion is creating new, cheaper submarines which may be just as effective in some situations as a nuclear powered variant and are providing an opportunity to countries

such as Israel to develop a submarine capability. China, Germany, France and even Russia are among those showing interest in this technology for its domestic or export potential and developments in hydrogen fuel cells will ultimately allow diesel-powered submarines to stay submerged while recharging their batteries.

So, with the Russian northern fleet once again flexing its muscles on operations in the Atlantic, and a Chinese 'Song' class turning up unannounced and entirely unexpected in the middle of a US exercise in the Pacific, the requirement for effective submarine-hunting capability is as clear as ever. As such the Royal Navy's Merlin HM Mk1, developed in Britain by Lockheed Martin UK to be the country's principal ASW asset, is destined to remain a key part of Britain's inventory for some time to come.

While the RAF's Merlin HC3 retains a primary focus on moving troops, weapons, ammunition and stores around the battlefield, the Merlin Mk1 - originally conceived as part of the Type 23 Frigate's weapon system - has widened its roles to include littoral surveillance, (in the shallows) troop movement, drug interdiction and search and rescue.

Of course its main focus remains ASW, and the Merlin Mk 1 can operate autonomously from a variety of ships, patrolling out at long range using its Blue Kestrel 5000 radar, Thomson Marconi Flash AQS 960 dipping sonar, GEC-Marconi sonobuoy acoustic processor and Racal Orange Reaper ESM to locate and identify submarines, and sting ray torpedoes and depth charges to engage them.