According to WENN, Mirren was eyed to play the royal as she joined Daniel Craig's James Bond en route to the Olympic Stadium via parachute.
Head of Ceremonies Martin Green told Britain's The People: "There were conversations about where we would take it if the Queen said no.
"We did talk about Helen at one point - but we didn't have to go to any other plan."
The London 2012 Olympic Opening Ceremony was directed by Trainspotting helmer Danny Boyle.
Kenneth Branagh, Rowan Atkinson and Russell Brand were among the stars involved in the opening and closing of the Games.
Watch Queen Elizabeth II and Daniel Craig in the Olympics 2012 Opening Ceremony sequence below:
Photo Gallery - Olympics best bits:
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