After 44 years, Lizzie's Britannia yacht was decommissioned in 1997, because the cost to keep it maintained was too much for the UK government.
According to Nina Myskow, Her Majesty was tearful at the farewell ceremony, remembering the happy times she'd spent with her loved ones on the grand vessel.
'The thing about the royal yacht was that it was an emblem of Great Britain,' the royal writer told UK TV presenter, Jeremy Vine.
'When it was decommissioned it was a big personal blow for her and I remember footage of the time, of the Queen with a tear coming down her cheek.
'It was quite devastating because you’d never seen the Queen like that before, it was a very personal thing.
'There’s wonderful footage of the Queen, the Duke of Edinburgh with the royals when they were young, really loving being on the Britannia because they were safe,' she explained to Vine.
'They were away from public gaze, they could actually be themselves. It was particularly dear to the Queen’s heart, they would sail around the UK or sail to Scotland in the summer.'
An unnecessary luxury in the eyes of the government, Myskow reminded audiences that the yacht did in fact play a huge part in promoting the UK to the world.
'It was used in all sorts of ways and PR things – they’d sail into the harbour somewhere and then the dignitaries would come aboard and they’d be hosted.'
She added, 'It was all very good for business, for trade and for the image of the UK and, at the same time, it was a very special place for the Queen.'