A very entertaining film, with fine performances by an excellent cast. Alec Guinness, as usual, plays the lead role impeccably. The addition of Noel Coward puts the "icing on the cake".
A complete farce, when a vacuum cleaner salesman is recruited to be a British spy, although quite why he is recruited leaves a lot to the imagination. Having no experience or interest in his new role (apart, that is, from the money it offers him), he finds it impossible to recruit "agents" to work for him. His charming, but totally irresponsible, daughter wants to live the high-life and who is he to deny her the opportunity to do so, merely because of a small thing called money!
Thus, he cleverly creates completely fictitious, potentially dangerous machines and installations, drawings of which he passes on to the British. They, of course, are most impressed and pretty soon he is paid even more money, because his results have become almost legendary.
Things begin to crumble about him, when he is assigned a secretary. There is some real action, where innocent parties are caught up in the web of intrigue and a murder (Burl Ives' character) is committed and another character is abducted. Hence, there is a slightly tragic, as well as humourous side, to the story.
The conclusion is a typical British farce, but I won't spoil it for you. I found the film enjoyable, very easy watching and definitely one I shall be enjoying in the future.