In this early series, the character of John Drake is clearly defined as being an American. When the character returned for the second Gioco pericoloso (1964) series, the character had become either British or Irish (exactly which was never settled upon definitively).
In the series' opening title sequence, the shot of Washington, D.C. is a composite of the Washington Capitol in the background and the Castrol Building, complete with London Bus stop, in the Marylebone Road, London as the foreground. This building is now the residential Marathon House having been converted from offices to flats in 1998.
John Drake says the phrase "I'm obliged" in virtually every episode. The catchphrase did not return in the 1964 series.
Virtually identical in format and style to the later Gioco pericoloso (1964) with two major differences: John Drake is an American in this series, and episodes include narration.
When Patrick McGoohan was shown a couple of early scripts, he demanded a few changes be made. The actor refused to allow Drake to become intimate with any woman, to use a gun as a means of killing, and to avoid making Drake a "one-dimensional muscle head".