Last June the Royal Navy nuclear ballistic missile submarine HMS Vengeance was executing certification training off the coast of Florida. Part of that training included the launch of a unarmed Trident II D5 submarine-launched ballistic missile—the same type that equips America’s Ohio class ballistic missile submarines. This event was the first Trident test launch by the Royal Navy in four years and was viewed not just as a way to gauge the readiness of Vengeance’s crew, but also the reliability of the UK’s nuclear weapons delivery system.

Reports state that the missile was meant to fly over 5,600 miles to a target off the coast of Africa, but instead went awry, flying in the complete opposite direction towards the US. The Times reports that the recently disclosed failure caused massive disruptions at the highest levels of government in London, and Downing Street decided to cover up the results of test through deep classification. While it’s known that the test failed, the reason behind the failure remains undisclosed.

The impact of this failed test within the UK has been dramatic. Just a month after the botched flight, Parliament voted on the future of the UK’s nuclear arsenal. This specifically included renewing its reliance on the Trident II missile system, and on the building of four new Successor class submarines to host them, a program slated to cost $50 billion. Without knowledge of the missile failure that occurred just weeks before the vote, the measure passed 472 to 117. Now, the relatively new Prime Minister, Theresa May, who was strongly in favor of the initiative, is in under fire for suspicions that she knowingly let the vote proceed without disclosing this important piece of information to lawmakers.

There may be reasons to keep a launch failure like the one that occurred last June secret, especially considering the Trident II and just four Vanguard class SSBNs represent the entirety of the UK’s nuclear arsenal. Such a launch failure degrades the credibility of the deterrent, especially at a time when increased tensions with heavily nuclear armed Russia is a reality. If it were disclosed that the missile’s failure was caused not by some errant malfunction or manufacturing error, but by the vessel’s crew itself, it could be even more damning. Still, not disclosing the failure, especially considering the political debate at the time, is leaving some well versed in London defense politics scratching their heads. Admiral Lord West, former first sea lord and chief of the naval staff stated:

“If a firing goes wrong you should say that it’s gone wrong, unless there’s something that means it’s so fundamentally wrong that it means the whole system is no longer viable otherwise we’re rather like the Soviet Union used to be, or like North Korea or China, where they won’t admit to things going wrong… I think it is bizarre and stupid that they didn’t say that there’d been a firing and that there’d been a missile malfunction, but it was a minor fault.”

The Royal Navy’s nuclear ballistic missile submarine program has already had more than its fair share of publicity pitfalls in recent years.At a time when the future of the force was being debated furiously in Parliament, knowledge of the such a missile failure could have swayed lawmakers to step away from the program entirely. Regardless, considering the timing of the botched missile test and the vote, classifying the failed test now looks suspect, no matter what the circumstances surrounding it. Yesterday, Prime Minister May was pressed about what she knew about the test and when, her only response was:  “I have absolute faith in our Trident missiles. When I made that speech in the House of Commons, what we were talking about was whether or not we should renew our Trident.”

Trident II was originally procured by Prime Minister Margret Thatcher from the Reagan administration in the 1980s. It, alongside a small fleet of cutting-edge ballistic missile submarines (which became the Vanguard class) were seen as a highly credible second-strike deterrent aimed toward keeping Soviet aggression at bay.

Some have suggested that the failure of the Trident II D5 missile, long thought to be among the most dependable and mature ICBM/SLBMs on the planet, also puts into question America’s own submarine-based nuclear weapons capabilities. Although a failure is never a good thing, especially considering the weapon involved could eradicate hundreds of thousands or even millions of people, the Trident II D5 remains a very reliable weapon system, with 161 successful test launches under its belt.

One of these tests happened just a few months ago, and over the last two years multiple Trident D5s have been launched, one of which resulted in major public attention. The US Navy plans on continuing to upgrade the Trident II, allowing the type to serve for decades to come. Additionally, the Columbia class nuclear ballistic missile submarines that are slated to replace the Ohio class in the coming decades are being designed around the missile. These new SSBNs are intended to serve well into the second half of the century.

Each Trident II D5 missile costs roughly $38 million, weighs 130,000 lbs, and has a maximum range estimated to be around 7,500 miles. That distance can decrease significantly with a full load of warheads and depending on the missile’s flight profile. Trident II can carry up to 14 warheads ranging in yield from the 100 kilotons (W76) to 455 kilotons (W88) in Multiple Independently Targetable reentry Vehicles (MIRVs).

Less warheads are carried in practice, due to START and now New START limitations, and to aid more flexible targeting; which may also allow for more decoys and penetration aids to be deployed during the midcourse phase of the missile’s attack. The exact nature of the Trident II’s countermeasure capabilities remains a closely guarded secret, but the UK in particular used decoys on their Polaris SLBMs under the name “Chevaline” before deploying the Trident.

A diagram of how Chevaline worked (wikicommons/Brian.Burnell):

Now that the heat is on the Prime Minister we’ll have to see if she moves to get the details surrounding the Trident missile failure declassified once and for all. Major media outlets and their undisclosed sources can report the details of these incidents incorrectly, and what sounds like a catastrophic failure could have been a much simpler issue, or not even a real failure at all. Even the direction of the missile and why it is flying in such a manner can be misinterpreted by reporters with limited knowledge of military operations. But without an official description of the incident to go by there is no way to correct inadvertently mistaken facts or give a more insightful analysis.

Certainly whatever is thought to have been the issue has been or is already in the process of being fixed, as both the UK and the US ballistic missile submarine programs depend on it. Still, a failure even of a nuclear tipped missile is bound to happen occasionally as the world has yet to find a perfect rocket system, even for space travel. And it may seem terrifying to some degree, but even in this day and age of highly reliable smart munitions, all expendable weapon systems have a failure rate, even those that can singlehandedly destroy entire population centers of the planet.

We will keep you updated as the story progresses.

Update- 1/22/17 1:20pm PST: CNN says that their source has confirmed the missile failure and stated that its “trajectory was part of an automatic self-destruct sequence. The official said the missile diverted into the ocean—an automatic procedure when missile electronics detect an anomaly.”