Curse of the mummy's tomb certainly is not a best effort from Hammer studios, as many of their true classics outshine it without any serious effort. However, it is not as much a disaster as many comments here in IMDb suggest. The movie doesn't have any Hammer's big stars in the cast, the story doesn't bring anything new into the mummy myth, and at few times the going gets unintentionally hilarious in the film. But on the other hand, the characters are acted quite solidly, even if the performances don't truly shine. Comical reliefs are mostly done with certain style, especially by Fred Clark as a P.T. Barnum replica, and the plot has few interesting twists. We even have here few scenes of surprisingly graphic of it's time, if a bit unrealistic screen violence, if that's your cup of tea. Slow pace and low action rate of the film works more for than against the movie, at least in my books, and the whole package is short enough, so the story can carry it all through till the end.
All in all, if you're a fan of old horror films, give it a go, whether you're a fan of Hammer studios works or not. At least this one certainly beats the stuffing out of it's follow-up, Mummy's shroud, which in my opinion truly deserves any public stoning it gets.
This is my truth - what is yours?