Five-year-old Zachary McCarthy-Fox has met the Queen so many times she comments on how he has grown.
Zachary and his royal-mad mother, Julia, also regularly camp on the pavement outside the Queen Mother's house to give her flowers.
They have even travelled as far as Denmark in pursuit of a regal hello.
Last Wednesday Zachary, his mother and grandmother, Jean Fox, went to Norfolk to give the Queen a hand-made card on the 50th anniversary of her ascension to the throne.
Two days later Zachary, of Ham Road, Worthing, received a letter from the monarch saying she had been "delighted to receive" it.
Zachary took it all in his stride. He said: "I thought it was quite nice of the Queen to send me the letter.
"She's my favourite. She said I looked nice. I normally look smart when we visit and I had on a smart shirt, trousers and a tie."
Zachary first met the Queen when he was 16 days old. He gurgled happily as she walked past during the Garter ceremony at Windsor.
Three years ago, he famously refused to give the Queen Mother a bunch of roses at Sandringham just before her birthday.
Zachary's grandmother, Jean, said: "The Queen Mother said to him: 'Are those flowers for me?' and he said: 'No. They're mine.'
"The Queen knows who his mum is and if they met in the street would know who she was.
"She has watched Zachary grow from a newborn baby and often comments on how much he has grown.
"He enjoys following the royals around and loves giving flowers to the Queen and Queen Mother."
Julia, 36, has been a keen royal-spotter since the age of 13 and attends at least 30 different royal engagements each year.
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