The Daily Mail reports that when filling out the Electronic System for Travel Authorisation (ESTA) immigration forms needed to enter the US, Mr Kenyon accidentally ticked 'Yes' instead of 'No' in response to the following question: "Do you seek to engage in or have you ever engaged in terrorist activities, espionage, sabotage, or genocide?"
The family was forced to make a 10-hour round-trip journey from their home in Poynton, Cheshire, to the US embassy in London so officials could interview young Harvey.
"I couldn't believe that they couldn't see it was a genuine mistake and that a three-month-old baby would be no harm to anyone," his grandfather told The Guardian.
"I went down with him and his mum and took him in for the interview, but he can't even speak as he's so young," the Daily Mail quoted Mr Kenyon saying.
"Baby Harvey was good as gold for the interview and never cried once. I thought about taking him along in an orange jumpsuit, but thought better of it," said Mr Kenyon. "They didn't appear to have a sense of humour over it at all and couldn't see the funny side.
The mix-up led to baby Harvey, his mother and her partner missing their flights to the US. Mr Kenyon said they paid an additional 3,000 pounds to re-book the airline tickets. The 62-year-old described the incident as a "very expensive mistake."
"If you were a terrorist, I suspect you'd not be ticking yes on the ESTA form anyway," he added.
The US embassy in London is yet to comment on the incident.
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