The Prisoner was filmed in the North Wales resort village of Portmeirion over the course of a year. Patrick McGoohan was inspired to film his series there after filming a couple of Danger Man (1960) episodes in the village.
Patrick McGoohan was adamant that Number Six not become romantically involved with anyone on the series (carrying over a policy he put in place for his John Drake character in Danger Man (1960)). Nonetheless, writers tried to pair Number Six up with female leads on a few occasions, only to have their efforts vetoed by Patrick McGoohan. The characters played by Nadia Gray in "Chimes of Big Ben" and Angela Browne in "A Change of Mind" were both written as love interests for Number Six, and there was reportedly a bed scene written for "Chimes" but McGoohan would have none of it. The closest Number Six comes to romance is in his friendship/simpatico with Alison in "The Schizoid Man" and in the character of an observer who falls in love with him in "Dance of the Dead."
At the end of the run of Secret Agent, there was a party, and some members of Parliament attended. Someone said to McGoohan, "So, what does a secret agent do when he retires?" meaning McGoohan. McGoohan took it literally and asked the question to some Parliament members. "Oh, we take care of them. We give them a house, a car, some pocket money, and that way they don't defect." This inspired McGoohan to create the show.
The building in Portmeirion shown as Number Six's house in the series became a gift shop selling Prisoner-related merchandise.
Due to the quirks of ITV's regional franchise, "The Prisoner" was not seen in North Wales (where the outdoor scenes were filmed) until 1970 when HTV bought it up.
George Markstein: The bald-headed man sitting behind the desk during the opening credits is the series' script editor and co-creator.