It seems 1960s Britain was very different from today. For some strange reason, the British Army thought it'd be a great idea to see what LSD did to its troops, and filmed the whole thing for you to laugh at 49 years' later.
Apparently the Army was interested in seeing if LSD could be used as a weapon to incapacitate the enemy. Judging by the reactions of these soldiers, I reckon it would have done the job nicely.
I'm not sure whether to be amused by these guys bumbling about in fits of laughter, or whether it's just a bit disturbing that we'd test these things on our own troops. And there I though that was the kind of thing that only happened in the movies. [YouTube via iO9]