"The most ghastly day of my life." The Queen's most harrowing memory in her 66 year reign.

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There’s been many a cause for celebration for Queen Elizabeth II and the royal family over the past few years; she’s seen two grandsons wed and welcomed great-grandchildren into the world.

But 66 years on the throne has not been without its dark times.

Dotted with terror attacks, wars and devastating deaths within the family, the Queen’s decades-spanning reign has been riddled with tragedy.

But there’s one harrowing memory which stands out amongst the rest as “the most ghastly” of all.

Flashback to July 20, 1982 – What started as a peaceful, sunny day in London took two explosions merely a couple of hours apart to become what the Queen now remembers as “the worst day of her life”.

The day of the Irish Republican Army’s attack on London, two bombs detonated in Hyde Park and Regent’s Park, killing 11 military personnel and seven horses, and injuring 50 civilians,

Andrew Parker Bowles, who oversaw the royal household cavalry at the time, remembers the terror of how it all unfolded.

In an interview with The Express, he said of the fateful day: “It was a nice, sunny day and suddenly one heard this explosion one heard all the time in Northern Ireland.

“One of the barriers opened and someone said, ‘They’ve blown up the Guard’. So we ran down to where the smoke was rising.”

The first devastating attack was during a Changing of the Guard ceremony in Whitehall, and took the lives of four soldiers and seven horses.

“The first horse I saw was Sefton. He had a bloody great hole in him but he managed to pull through,” Parker Bowles said.

But that wasn’t the end of it.

A second blast occurred just a couple of hours later under the bandstand at Regent’s Park, where the British Army’s Royal Green Jackets were entertaining 120 people enjoying a day out in the July sun.

Seven members of the band were killed, and several others wounded.

Parker Bowles, who was married to Camilla, now the Duchess of Cornwall, at the time, had a memorable conversation with the Queen in the wake of the attacks.

“She said to me it was ‘the most ghastly day of my life’.”

Five years after the terrifying day in October 1987, Gilbert McNamee, who was just 27, was sentenced to 25 years in prison for his role in the Hyde Park bombing, but was later found wrongly convicted and released in 1998.

IRA member John Downey was also charged – but never went to trial – with four counts of murder. According to previous reports by The Guardian, he is still a suspect, but walked free from trial again in 2014.

Last year, relatives of those killed in then IRA attack held a march in London to demand justice for their families.

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