It wasn’t.

What happened? The error was reportedly a problem with the “data acquisition system” forcing a range controller to terminate the flight test, diverting the missile into the ocean as a safety precaution, we understand this is an automatic procedure when the systems electronics detect an anomaly.

The Sunday Times reported on that a Trident II D5 missile “veered off in the wrong direction towards America” after being launched from HMS Vengeance. It should be noted however that a range in the US was actually the target and that the new trajectory that forced the missile into the ocean was part of an automatic sequence designed to bring down the missile when anomalies are detected during testing, not a guidance failure.

The problem was with telemetric directional data, i.e. faulty information being received from the missile. The test was part of a demonstration and shakedown operation that saw HMS Vengeance returned to service in the same month, June last year.

Paul Ingram, executive director of the British American Information Council told the Guardian that the telemetric data issue suggests a minor error, rather than a failure on the part of the rocket engine or guidance.

“It is a complex system. It is an amazing feat of human engineering but everything has to work or there is catastrophic failure and a catastrophic failure can have catastrophic consequences.”

A Government Spokesperson said:

“The capability and effectiveness of the Trident missile, should we ever need to employ it, is unquestionable.

In June the Royal Navy conducted a routine unarmed Trident missile test launch from HMS Vengeance, as part of an operation which is designed to certify the submarine and its crew. Vengeance and her crew were successfully tested and certified, allowing Vengeance to return into service. We have absolute confidence in our independent nuclear deterrent.



We do not provide further details on submarine operations for obvious national security reasons.”

Former Rear Admiral Chris Parry told the BBC:

“Quite a lot of these shots nowadays are being done to test the limits of the system, so that we can get the next generation of ballistic missiles in.

“It may well be that they were testing this missile close to its flight limits, so they could see where it wasn’t going to work.”

Speaking to The Sunday Times, Labour MP Kevan Jones said:

“The UK’s independent nuclear deterrent is a vital cornerstone for the nation’s defence,” he said. “If there are problems, they should not have been covered up in this ham-fisted way.

“Ministers should come clean if there are problems and there should be an urgent inquiry into what happened.”

HMS Vengeance is the fourth Vanguard class submarine and carries the Trident ballistic missile, the UK’s nuclear deterrent. The vessel sailed from Devonport after refit in December 2015 and then went through trials from January 2016 to June 2016 and fired the unarmed D5 missile towards a range in the US during trials which then allowed her to return to the fleet.

MPs are demanding an inquiry and are calling for a Commons statement from Defence Secretary Michael Fallon on Monday.

Trident still remains the most reliable ballistic missile system in service anywhere in the world.

Who controls Trident?

One of the most common myths around the system is that the United States has control over the UK’s Trident missile system, that is not the case.

It’s often said that the UK’s Trident nuclear weapons system is not ‘independent’ or that the UK doesn’t have the ability to use the system without the US agreeing to it, in reality the UK does retain full operational control over the system.

One common argument is that the US can simply ‘turn off’ the GPS system and therefore can stop the UK using Trident, this is also a myth, Trident isn’t guided by satellite.

The missile uses a kind of stellar sighting guidance system and inertial navigation to take a reading from the stars to work out the missile’s position and make any adjustments necessary. They do not require GPS.

One source for the confusion could be the fact that, aside from those currently deployed, the missiles are held in a communal pool at the US Strategic Weapons facility at King’s Bay, Georgia, USA where maintenance and in-service support of the missiles is undertaken at periodic intervals.

The missiles are jointly maintained, this is much cheaper than the UK doing it on its own and does not give the United States control over any of the weapons deployed on the submarines.

Does the system require American codes to launch?

American operated Trident missiles are controlled through the US Navy chain of command by the US President. ‘Permissive action link technology’ prevents anyone other than the president or someone he has delegated control to authorising a launch.

In 2007, the UK Government revealed that its nuclear weapons were not equipped with Permissive Action Links. Instead, the UK’s nuclear bombs to be dropped by aircraft were armed by just inserting a key into a simple lock similar to those used to protect bicycles from theft, the UK withdrew all air-launched bombs in 1998. The current UK Trident warheads can also be launched by a submarine commander with the support of his crew without any code being transmitted from the chain of command.

The British missiles are controlled through the Royal Navy chain of command all the way up to the Prime Minister. In reality the Prime Minister would make the launch decision in concert with whatever was left of the British government.

The key point here is that the British deterrent does not have permissive action link control, which means it does not rely on the use of codes to fire the system. The UK’s Trident fleet relies purely on military discipline to prevent a launch.

In summary, the UK retains full operational control, to the extent that the US could not stop the UK from using the system. A Freedom of Information request proving that the United Kingdom has full operational control over its Trident missile system can be downloaded here.