Some Cold War history for a Sunday

I didn't know this:  the BBC ran a radio show up to 1974 (not sure when it started) in which they would read out letters from unidentified people in East Germany, detailing their life and suffering there.  This sent the East German secret police nuts, who went to extraordinary lengths to track down the writers:

The Stasi not only viewed the BBC as an enemy broadcaster, they specifically saw this programme as a form of psychological warfare aimed to destabilise the regime and incite resistance. They were convinced Harrison was an undercover spy, wooing agents in East Germany.

In the end it was the letter writers they really knuckled down on, and the Stasi were extraordinarily fastidious in their pursuit.

They took saliva samples from the licked envelopes to identify blood groups which they cross-checked with doctor's records. They traced fingerprints on the paper, sourced the ink and collated an extensive archive of handwriting samples. 

It was his handwriting that caught out Borchardt.

"It just seemed like an ordinary piece of homework," he says, when the pupils in his class were asked to write an essay describing themselves and their later goals in life.

"The thing is, my father thought I had such terrible handwriting he wanted my sister to write it up for me. He nearly got his way."

As ordered, the school passed the essays on to a Stasi agent. Documents show a painstaking analysis of every curve and stroke of Borchardt's pen, comparing it to the intercepted letters from the anonymous schoolboy.