Fleming had Bond as a debonaire upper class type who would pass for the curator of an art galley, and not appear to be a macho, rough hewn, action man. The idea was that he didn't look like a spy, but someone who is at home with the elite, travelling often, and being seen around the part of London where MI6 is located, without drawing attention to himself.
Incidentally, Fleming had trouble coming up with a name for his character. He was living in Kingston, Jamaica, before Youtube was thought of. So going out to talks from visiting experts was something to look forward to. He attended a lecture by an ornithologist, specialising in Caribbean birds. When the fellow got up and introduced himself, he is reported to have said "my name is Bond; James Bond" and that clicked with Fleming, who wanted a dull name for his spy.