The Royal Signals major positioned to press the detonator had done so prematurely, with the fuse lit by the monarch still fizzing about 60m away.
"Can't think why you bothered to ask me!" she had said with a laugh.
The sound system had started to fail and a deafening firework mortar had gone off instead of a flare.
Parker explained: "'Your Majesty', I said, 'I'm afraid it's all going terribly wrong'. Her face lit up. 'Oh good,' she said. 'What fun'!
"I feel sorry for her, having to watch so much dreary stuff all the time. Anything that keeps you awake and makes you smile must be a good thing.
"The Queen is always amused by cock-ups, as long as they're not serious. Most people would not notice the things that go wrong.
"She doesn't miss a trick," said the 71-year-old.
- AAP