Eighteen-month-old Charlie - who bears a strong resemblance to the Queen’s great grandson Prince George - handed over a posy, made by his mum Alexandra, to the smiling monarch.
The encounter happened when the Queen visited the Windsor Royal Mail delivery office on Wednsday.
Charlie’s grandad Derek Warner, 69, had been invited with his wife Beverley and family to be part of the royal visit to mark his 50 years’ service with Royal Mail.
Derek, who lives in Kingsley Road, Horley, said: “When the Queen’s car arrived, one of the aides asked if ‘the little boy’ would like to present his flowers to the Queen. My daughter, his mother, said that would be fine.
“The Queen went in to the delivery office to unveil a plaque.
“I sat there with Charlie but he kept wandering off and wanted to get in the (Queen’s) Bentley.
“Eventually, when the Queen walked out, I thought it was going to be a nightmare. There were about 300-400 people there. But, on cue, I handed Charlie the flowers and said ‘Give them to the lady.’
“The Queen said ‘Isn’t he small’? ... I was gobsmacked.”
He said he was trembling before the encounter in case the Queen asked him any questions, but it all went smoothly.
And the Queen wasn’t the only celebrity that Derek and his family met in Windsor that day.
“We went for coffee with some Royal Mail people after the Queen’s visit and then had lunch at a local pub,” said Derek.
“We finished the day by wandering round Windsor and ended up meeting Sandra and Sandy from the TV programme Gogglebox. They were good fun. It was a lovely day.”
But the day didn’t end there for little George. On Thursday, a reporter from The Sun newspaper contacted Derek to ask if the paper could take some more photos of George, thought to be the youngest person ever to be presented to the Queen.
Charlie was taken to clothes designer Rachel Riley, from where Prince William has bought clothes for Prince George, and kitted out in right royal attire.
“I couldn’t believe it when I saw him,” said grandad Derek. “He was Prince George’s double.”
Derek, who first started working with the mail service when it was known as the GPO, now works at Royal Mail’s Gatwick centre.