The 51-year-old, who also regularly appears on television, was enjoying a long walk with his 11-year-old when a squad car and a police van stopped him on a Yorkshire roadside.
Self, author of Great Apes and The Book Of Dave, was questioned about what he and the schoolboy were doing out walking together and his details were checked on the Police National Computer, he said.
Self, an enthusiastic rambler, and his son set off in July from London to Whitby, north Yorkshire, on their walking holiday. "No Englishman enjoying a ramble with his son should face examination by police at the roadside on suspicion of being a sexual predator," he said.
Wearing full rambling gear and with his son carrying a walking staff, they crossed the Humber Bridge after 11 days on foot and were aiming to reach a bed and breakfast in North Dalton. To shave some time off their walk while in Bishop Burton near Beverley, Self asked a security guard at an agricultural college if they could cut through the establishment's grounds. His answer was a firm no.
Self said: "The insinuation that I might pose some sort of threat to young people - in a word, that I might be a paedophile - was underscored by his eyes then sliding to my drooping son. He was being absurd and offensive."
The security guard reported him to the police who drafted in a specialist officer from 30 miles away.
The college was unavailable for comment.