Now, the true story behind that fated message – and where it came from – can today be revealed.

It all began on Sunday evening, when a screenshot from a WhatsApp group conversation began circulating on Facebook and Twitter.

In it, one user, known only as ‘Gibbo’, wrote: ‘Queens passed away this morning, heart attack, being announced 930 AM tomorrow (sic).’

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Queen Elizabeth II is seen at the Chichester Theatre while visiting West Sussex on November 30, 2017 in Chichester, United Kingdom. (Photo by Stuart C. Wilson/Getty Images)

The group chat – which also includes users named ‘Burnsy’, ‘Cheeks’, ‘Josh’ and ‘Morty’ – was understood to have been between serving military personnel.

Gibbo continued, writing: ‘Channel dash 0800 tomorrow in full number 1s, in your black kit bag you need: 1 set of 3s 1 set of 4s Underwear and socks for 2 weeks (sic).’

Within 24 hours it had been shared by thousands of people worldwide, with hashtags #GodSaveTheQueen, #QueenDead and #BuckinghamPalace trending on Twitter.

Buckingham Palace was even forced to respond after speculation reached fever pitch, with a royal spokeswoman downplaying the rumours and saying it was ‘business as usual’.

The WhatsApp chat that led to the social media storm about the Queen's 'death'.

Now, The News can exclusively reveal a weekend drill at a Royal Navy base was at the centre of the social media storm.

Personnel based as Royal Navy Air Station (RNAS) Yeovilton had been practising for an Operation London Bridge recall – the codename used for when the Queen dies.

It is believed that someone received the exercise recall message and, thinking it to be real, then forwarded it on further.

It’s not known whether any of the users in the WhatsApp group were serving in the navy. However, the Senior Service insisted the oversight was a ‘genuine mistake’ and that ‘no malice’ was intended.

Speaking to The News, a Royal Navy spokesman said: ‘We can confirm an internal exercise took place at Royal Naval Air Station Yeovilton in line with established contingency plans for recall of personnel.

‘These exercises are conducted on a regular basis and no significance should be drawn from the timing of the exercise.

‘While the exercise was conducted properly, we regret any misunderstanding this may have caused.’

Former paratrooper Alfie Usher shared the initial WhatsApp message to his army of Facebook followers on his Fill Your Boots UK military humour page.

Mr Usher, who runs military insurance firm Forces Compare, claimed he didn’t believe the message was real and insisted he shared it as a joke on his page, which is followed by 97,413 people.

However, shortly after posting it, he was bombarded with questions by people fearing it was a genuine message and was forced to delete the original post and write a clarification about it.

Speaking to The News, he added: ‘It went bigger than Ben Hur.

‘I realised I was losing control of the situation when other news sources were picking it up.’

Mr Usher claimed he never believed anyone would believe the post on the page, which regular shares military-related jokes and humour.

He added: ‘I feel so sorry for Gibbo. Someone screenshotted his message which was out of his control and but he will be the one that gets shafted.’

RNAS Yeovilton is one of the navy's two principal air bases, and one of the busiest military airfields in the UK.

It is home to more than 100 aircraft operated on both front-line squadrons and training units, including the Fleet Air Arm Wildcat Force and the Commando Helicopter Force.