Without any narration, it’s the soundtrack that is left to be the voice of this potted history of Czechoslovakia as it was annexed by Hitler, freed by the Soviets, had a brief time of relative peace and prosperity and then, in 1968, their erstwhile rescuers - as poignantly illustrated by a cartoon here - returned with their tanks and guns, only this time they were there to stay. It’s barely a quarter of an hour long, so barring a few significant images of the early days and the Nazis, it really focuses with an impressive array of archive on the invasion and of the protesters determined to hold ...