UK's Trident nuclear-deterrent missile system misfires during test

By William James

LONDON (Reuters) -Britain's Trident nuclear-deterrent system misfired during a test last month, sending a missile crashing into the ocean off the Florida coast near the submarine that launched it, The Sun newspaper reported on Wednesday.

The Ministry of Defence confirmed an 'anomaly' had occurred during the test but said the country's "nuclear deterrent remains safe, secure and effective."

With defence secretary Grant Shapps on board the HMS Vanguard to witness the test, The Sun said the first-stage boosters on the missile - equipped with dummy warheads - had failed to ignite.

The result marked the second successive test failure of a Trident missile after one was reported to have veered off course in 2016, an embarrassing outcome for a country that once boasted the largest and most powerful naval force in the world.

"It left the submarine but it just went plop, right next to them," The Sun quoted a source as saying.

While the MoD said in a statement that an anomaly had occurred, it said it was "event specific" and had "no implications for the reliability of the wider Trident missile systems and stockpile."

The government could face questions in parliament over the failure, and the fact that it was first reported by the media rather than by ministers, at a time when the readiness of Britain's navy has been under scrutiny in the event it is drawn into a full-blown conflict.

Earlier this month, one of Britain's two flagship aircraft carriers, the HMS Queen Elizabeth, had to be withdrawn from the largest NATO exercise since the Cold War after routine checks identified an issue with a propeller shaft.

Matthew Savill, director of Military Sciences at the Royal United Services Institute, a defence and security think tank, said the government was unlikely to provide many details - due to security reasons - about the test on HMS Vanguard, which had recently undergone a 7-year refit.

Savill said that nuclear powers watch each others' tests.

"China and Russia will have been looking out for this, and they will have almost certainly detected that there was not a (successful) missile launch," he said.

Britain's nuclear deterrent is provided by a fleet of four nuclear-powered submarines which are equipped with the Trident ballistic missile system, manufactured by Lockheed Martin.

The nuclear deterrent system costs around 3 billion pounds ($3.79 billion) per year to operate - equivalent to roughly 6% of the UK's overall defence budget. Parliament voted in 2016 to approve building a new class of submarines, due to enter service in the 2030s, at a cost last estimated at 31 billion pounds.

RUSI's Savill said that meant the Vanguard fleet was operating beyond its expected service life, explaining why the submarines were requiring lengthy refit programmes.

"They're working on the basis that the Vanguard submarines are going to be at least a decade beyond their original service lives," he told Reuters. "And that creates stresses and strains on the system."

According to the Royal Navy website, there has always been a British ballistic missile submarine at sea since 1969, and that "a credible nuclear deterrent depends on the ability to threaten an assured and effective response to aggression."

($1 = 0.7920 pounds)

(Reporting by William James; Editing by Paul Sandle, Andrew Heavens and Bernadette Baum)