The 68-year-old actress portrayed Her Majesty in the final two seasons of Netflix's royal drama - gaining nominations for the British Academy Television Award for Best Actress and Golden Globe Award for Best Actress for her work - and said she and her castmates were warned on set just before the monarch's passing aged 96 in September 2022 was announced there may be "bad news" on the way.
She told The Daily Telegraph about breaking down when it was confirmed the Queen was dead: "We'd filmed in the morning, then at lunchtime the first AD (assistant director) came up to me and said, 'We just have to warn you, we might hear some bad news later.'
"He said, 'Do you want to carry on or go home?'
"I said, 'No, I'll carry on.'
"And then we went home at 6pm, and the news came, and I was completely inconsolable.
"The ground really was shaking. So that was new territory for me."
Filming was suspended on 'The Crown' for the 10 days of national mourning for the late monarch, and resumed the day after the Queen's funeral.
It started with Imelda shooting a scene of the Queen unveiling a plaque and she said it was "difficult" for her castmates to see her dressed as the dead monarch.
She added: "We had a number of supporting actors that day, and they were looking at the Queen, and I think that was more difficult for them than it was for me. I do remember it was very quiet on the set".
Imelda added playing the Queen was "a great place to be" as it put all her skills to the test.
She added that as research for the part she buried herself in "watching footage, working on her voice, movement, things like that - absorbing her somehow".
The acting veteran told the Telegraph: "Being the Queen was a great place to be... being wholly another person is a very interesting journey.
"As an actor that's what we do, and you want to bring everything you can to it, but some parts don't demand that."
Imelda received a coveted damehood in King Charles' Birthday Honours List earlier this month after a career of more than 40 years that has seen her reach national treasure status thanks to roles in projects from 'Harry Potter' to 'Vera Drake', in which she played the famed backstreet abortionist.