The island which Simon and Marla look down on (as they fly out to visit Dr Krayford), isn't really a Carribbean island, it's the Isle of Luing in Scotland.
There are several remarkable similarities between Island of Chance (1967) and the first half of the James Bond film, Dr. No (1962).
The island setting, the calypso club and the girl with the camera, the assassination attempt at night using a poisonous creature and the Grant characters similar to Quarrel.
Actor Tommy Eytle also portrayed a calypso singer in another classic ITC series of the period; Danger Man (known in the States as Secret Agent (1964)) and the songs he sang were the same as well. Moreover, the incidental music (by the inimitable Edwin Astley) used in both series (who worked on both) is the same - more-so in certain episodes, such as this one.
A very odd (and rare) occurrence; for some odd reason, Canadian actress Suzanne Lloyd and British actress Sue Lloyd were the guest stars in consecutive episodes.
Unlike every other episode, when Templar's introduced, it's not in the slightly cheeky, admirable or flippant way. Usually he's recognised and someone says some variation of '...the famous Simon Templar', with him usually looking directly at the camera and raising an eyebrow, followed by the opening theme. Instead, Templar's friend has just been killed in front of him. When the club photographer (Sue Lloyd) asks who the man was, Simon grimly says, 'his name is Frank Cody. Mine's Simon Templar'.