For many years, Up the Khyber was rated as the best of the Carry On series. There's a decent location shoot, with Snowdon, Wales standing in for the North West Frontier, Afghanistan, and reasonable production values. The plot is typically absurd, but more robust than usual.
While there's the standard barrage of smutty double entendres, a few still raise a titter and they are not as threadbare as some later entries. The cast of regulars isn't quite at full strength- Kenneth Connor is always missed- but most of the key names are present and Joan Sims is in good form as the vulgar wife of the Governor (Sidney James).
It's a spoof of those historical adventure films about the British in India during the height of the empire. Which would have been fair game to the cast and crew at the time, but now will be problematic to some. So there are silly puns made of Indian names, with Bernard Bresslaw as Bungdit Din. Half of the cast is in brownface.
So what was once the jewel in the crown of the Carry On series, now feels among the most compromised. If all that is set aside... this is genial, unpretentious stuff which really doesn't mean to offend. It seems unlikely that these films are still being watched half a century on. But compared to other lowbrow comedies of the period, this one stands up fairly well.