The Secret of My Success (1965)

Thanks to his mother's help, Arthur Tate somehow makes a remarkable rise from a lowly constable to the ruler of a South America country.

His story begins with Inspector Hobart's investigation into dressmaker Violet Lawson's missing husband. Hobart suspects foul play and digs up Violet's cellar, looking for the body. Violet did indeed kill her spouse, but doesn't bury the corpse there until after Hobart has dug the hole. A helpful tip from Arthur's mum makes him the hero who solves the case.

Baron von Lukenberg is then arrested for creating a species of deadly spiders. But it is actually his wife, the Baroness, who is responsible. Arthur, with his mum's aid, once again saves the day. President Esteda of the South American nation of Guanduria is so favorably impressed, he hires Arthur to be his personal liaison.

Marigold Marado turns up, telling Arthur she wants to make a film about his heroism. What he doesn't know is that Marigold is a revolutionary who hopes to overthrow Esteda's government. The film she ends up creating inadvertently turns Arthur into a great revolutionary hero, and it is he who becomes Guanduria's new leader.

Arthur can do no wrong. The Earl of Aldershot learns of his great deeds and leaves Arthur the grand sum of 15 million pounds in his will. Arthur goes back to England to the Earl's mansion to collect, but by now Mrs. Tate has had quite enough. She blows up the mansion with her son in it.