http://www.bbc.co.uk/dna/h2g2/alabaster/A163108
In the 40s and 50s, the Civil Service instigated a plan to lace the nation's tea with a mind control drug to prevent the populace fretting about things like nuclear war; and deteriorating Test match results. A tea shortage would have caused mass panic.
"The medium for distribution of the drug was a simple choice. All foods were strictly rationed, and tea was the only beverage readily available in Britain (apart from gin and beer, which were obviously out of the question for the abstemious bureaucrats). In addition, the quality of tea had deteriorated due to poor supply from India, so the rather metallic taste of the drug was unlikely to be noticed."