More soap opera than true crime, but this cinema advert is almost as cunning as its onscreen detective.

The mystery of the bogus brother burglar - a case for Sherlock Foams? Like many of the best cinema ads from this period, the puzzle for audiences was how the carefully crafted story was going to twist into a sales message. The reveal here is distinctly clever, as the clue that cracks the case highlights the USP of the product. Elementary, my dear Persil.