Her stoic, unshakeable nature was the cornerstone of her 70-year reign. But even Queen Elizabeth II had her limits – and, as it turns out, there was one rare moment when the pressure became overwhelming.

This compelling, little-known piece of Windsor history was revealed by renowned royal author Robert Hardman during a live recording of HELLO!’s A Right Royal Podcast. Speaking at the exclusive HELLO! royal event about his new book Elizabeth II, Robert detailed how the Queen, then 43, suffered a period of “nervous exhaustion” that the Palace successfully kept hidden from the public for decades.

The year was 1969 – a period Robert describes as a “turning point” for the monarchy. While the “Swinging Sixties” were in full bloom, the Royal Family was struggling to stay relevant, eventually allowing cameras into their private lives for the landmark Royal Family documentary.

However, behind the scenes, the pressure was mounting. The primary cause of the strain was the investiture of Prince Charles as the Prince of Wales. While the event was a television milestone – the first major live event broadcast in colour – it was overshadowed by a terrifying wave of separatist violence.

Watch: The late Queen’s secret breakdown revealed

“It was getting really ugly and bombs were going off,” Robert explained to the live audience. “People had been killed in the run-up to the investiture. It was a really tense few days.”

The “Summer Flu” Cover-up

The stress reached a climax during the journey to the ceremony at Caernarfon Castle. Robert recounted the chilling moment the royal party heard a “bang” – another bomb detonating nearby. For the Queen, the combination of physical danger, the weight of the first-ever global TV broadcast, and the political unrest proved too much.

Upon her return to London, Her Majesty did something entirely out of character: she cancelled her diary, including her beloved trip to Wimbledon, and took to her bed.

1st July 1969:  Queen Elizabeth II crowns her son Charles, Prince of Wales, during his investiture ceremony at Caernarvon Castle.  (Photo by Hulton Archive/Getty Images)
© Getty ImagesStress was at an all-time high for Queen Elizabeth during the investiture ceremony of the Prince of Wales at Caernarvon Castle on July 1, 1969

“The Palace put out a statement saying that she was suffering from what they called ‘summer flu,'” Robert revealed. “But, as I was told by someone very senior, it was actually nervous exhaustion.”

The impact was so significant that 1969 became the only year of her reign in which the Queen did not record a Christmas broadcast, opting instead to repeat the documentary.

Andrea Caamano, Robert Hardman, Emily Nash and Emmy Griffiths recorded a live podcast about the late Queen© Alex IngramAndrea Caamano, Robert Hardman, Emily Nash and Emmy Griffiths recorded a live podcast about the late Queen

This revelation was just one of many shared during our exclusive live event. From the Queen’s private fears for her children to the secrets behind Robert’s latest book, the full conversation is a must-watch for any royal follower.

How to watch the podcast episode

Watch the full episode of HELLO!’s special live A Right Royal Podcast episode below:

WATCH: A Right Royal Podcast live

Robert Hardman’s new book – Elizabeth II: In Private, In Public, The Inside Story – is published ahead of what would have been Queen Elizabeth II’s birthday later this month.