Hammer's 'The Mummy' had its genesis in the huge success of both 'The Curse Of Frankenstein' and 'Dracula' - previously sniffy about the use of 'their' characters, Universal Studios suddenly saw the light (and the royalties) and gave Hammer carte blanche to remake whatever they wanted from their portfolio of classic horror films.
'The Mummy' isn't a straight remake of the 1932 Boris Karloff film, instead recycling bits and pieces from its sequels, as well as adding colour, extra violence and moving most of the action to Britain. The familiar themes of love across the centuries, reincarnation and ancient curses are naturally present, with The Mummy wreaking deadly vengeance on the archaeologists who discovered / desecrated Princess Ananka's final resting place. Christopher Lee has a dual role: as Kharis, the High Priest in love with Ananka who is sentenced to a living death for his blasphemy in trying to bring her back to life, and as The Mummy itself - an unstoppable tool of revenge, impervious to bullets, incredibly dessicated and scuzzy looking - but, four thousand years on, still in love with his Princess and Peter Cushing's wife who just so happens to look just like her.
A massive box office success, 'The Mummy' eventually spawned three semi sequels (there is no relation between them apart from the Egyptian theme), including the supremely daft 'Blood From The Mummy's Tomb'. Good stuff.