by Douglas Barrie, PA Wire

A SPECIAL parade involving hundreds of service personnel has been overseen by the Princess Royal as HM Naval Base Clyde marked 50 years of housing the UK's nuclear deterrent.

The Continuous At Sea Deterrent (CASD), also known as Trident, has been operated by the Royal Navy Submarine Service at Faslane near Helensburgh since 1969.

Around 400 serving men and women from 17 platoons took part in the parade on Friday, with an estimated 800 of their friends and family watching on.

It is thought to be the biggest single gathering of Royal Navy submariners since the Second World War.

In a letter printed in a special programme for the day, the Princess Royal paid tribute to the submarine crews, industrial partners and civil servants.

READ MORE: Submariners mark 50 years of Navy's 'ultimate mission'

She wrote: "The achievement that this milestone marks is truly incredible and yet, delivered as it is by the 'silent service' the scale of this endeavour is too often overlooked by the very population that you have defended every day for the last 50 years."

The sentiment was echoed by Lord Boyce, admiral of the fleet, who also recalled his first experience of the area.

He said: "When I first came to Faslane there was nothing here at all, there was just the depot ships sitting alongside a jetty, so all the concrete you see here now, the buildings were not here.

"It's a transformation of this particular area over a long time.

READ MORE: Submariners celebrate service's birthday at Faslane

"I think the submariners have always been professional in what they do but now they're super professional and I think we could see that today.

"Of course lots of young people will be seen on parade today and I'm very proud to wear a submariner badge myself."

During the parade the brass band played songs with Scottish links, from the traditional Highland Cathedral to Sir Rod Stewart's aptly-named Sailing.

Some included in the ceremony included the crews of HMS victorious, HMS astute, HMS Neptune and veterans - as well as members of the US Submarine Service with one of their subs docked in the base.

The Princess Royal also handed out a number of special pins recognising terms of service to several submariners and staff.

READ MORE: Royal Navy sailors salute 50 years of service on the Clyde

One of those was Chief Petty Officer Karl Davies from west Wales, who received a gold deterrent patrol pin for making 20 such excursions.

He said: "I've just completed 22 years, all here at Faslane. It's a massive change, particularly in the infrastructure.

"When I first came up the accommodation was all different from now - there's good accommodation, sports equipment and the sports centre is really good.

"It was an honour to receive the pin but it was more of an honour in the fact that my family have travelled up from west Wales to see it as well and be part of it.

"Because this isn't just about me - this is about them, too."

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He added: "I think (Princess Anne) was in a bit disbelief that 20 patrols equates to roughly 10 to 11 years of underwater, so I think she found that a bit of a shock.

"But she also reiterated the importance of how family are there to support and it's always nice to come back and have that welcome return."