PREDICTABLY the Government has chosen to hide behind that old chestnut ‘national security’ to hide its embarrassment over the Trident missile launch that went wrong.

The Prime Minister and Defence Secretary would like us to think this was a routine test. It was not.

Trident missiles are so expensive – each one costs £17m – that there have only been 11 test firings since the first Vanguard class boat entered service in 1994.

Sir Michael Fallon told the Commons yesterday: “It has never been the practice of governments to give Parliament details of... shakedown operations.”

A missile test launch is the final stage in trials before a Vanguard class submarine returns to active service. Previous – successful – launches were widely publicised. The Ministry of Defence issued photos and videos of the last missile firing, by HMS Vigilant, in 2012. They are widely available on the internet.

Sir Michael tried to argue that times have changed and publicity now would be useful to Britain’s enemies.

But the abortive test by HMS Vengeance was well known in advance (the MoD warned pilots in the area of an impending missile launch three days earlier) and it would be naive to assume Britain’s enemies were not watching.

We do not think the MoD should give a running commentary on the operational effectiveness of Britain’s naval forces.

However, in this case we do believe it owes the country an explanation.

The Trident independent nuclear deterrent is the most powerful weapon in the UK’s arsenal. Everyone prays that it will not be needed but, if it is, it must work first time, every time.

We need to know what went wrong and, more importantly, why Trident will not go wrong in the future. After all, there are no second chances in war.