I seem to remember that the Twin Pioneers based in Sharjah in the '60s were fitted with a simple drift sight very similar to those mentioned so far. And although I don't remember seeing it, the Shackletons would probably have had one too, wouldn't they?
The Twin Pin one was very easy to use; you just rotated the scope tube until the hairlines lined up with the apparent direction of travel over objects on the ground, and then read off the drift angle from a scale. In hazy conditions, though, it was sometimes difficult to see the ground clearly enough. At night, the moon gave enough light if was big enough, and the occasional Bedu camp fire was useful.