William told of sacrifice that has delivered 50 years of nuclear deterrent

The Duke of Cambridge and new Defence Secretary Penny Mordaunt have heard of the pride and sacrifice that has gone into delivering five decades of Britain’s continuous at-sea nuclear deterrent.

Since April 1969, for 24 hours a day, seven days a week, 365 days a year, at least one UK ballistic missile submarine has been on patrol beneath the waves of the world’s oceans.

William and Ms Mordaunt, in what is believed to be her first official engagement since becoming Defence Secretary this week, were at a Westminster Abbey service to recognise the commitment of the Royal Navy in maintaining Operation Relentless – the longest mission in the history of the services.

Protesters pinned back by a security cordon shouted various chants, including “Down with Trident” and “Down with War”, as they arrived and later left the building.

William and Ms Mordaunt joined a 2,000-strong congregation, largely made up of naval representatives and their relatives, at the service.

William and a relaxed-looking Ms Mordaunt, who is a Royal Navy reservist and the first woman to hold the position, were each greeted on their arrival by the Dean of Westminster, the Very Reverend Dr John Hall.

Ms Mordaunt had earlier announced that the fourth Dreadnought submarine is to be named HMS King George VI.

She added: “We pay tribute to those incredible crews, their supportive families, the Royal Navy and the thousands of industry experts who will continue to sustain this truly national endeavour for many years to come.”

Gavin Williamson was sacked as defence secretary this week despite his “strenuous” denial that he was responsible for the unprecedented leak of information from the National Security Council.

The Dean told the congregation of the repeated calls he had received, including messages just last night, for the service to be abandoned.

Critics stressed that the work of Jesus was about peace, not violence, he said.

The Dean said “clearly we have not done so and are proud to be holding it here in the Abbey”.

He said: “The only legitimate aim for any country’s military capability is securing peace.”

He added: “I have been asked repeatedly whether this service was meant to be a celebration of nuclear weapons, or an act of thanksgiving.

“We can’t celebrate weapons of mass destruction, but we do owe a debt of gratitude and sincere thanks to all those countless men and women, some represented here today, who in the past 50 years have maintained a deterrent, and indeed to their families, who have stood by them.

“Those countless men and women played their part, a vital part, in maintaining peace.”

The Dean spoke of the “terrifying force” and the “massive devastation” which can be inflicted by nuclear weapons.

He also spoke of the 1945 bombing of Hiroshima.

William, as commodore-in-chief of the submarine service, gave a reading during the service.

He wore a dark suit which had the Queen’s Golden Jubilee medal and the Queen’s Diamond Jubilee medal pinned to it.

Rear Admiral Tim Hodgson, the Ministry of Defence’s submarine capability director told the congregation: “The boats themselves are the work of a nation, set to task five decades ago to deliver complex machines at the forefront of modern-day technology.

“People across the country are united in an often unseen, quietly acknowledged purpose of delivering our deterrent and the surety it brings.”