UK spy agency MI5 reveals fruity secrets in new show

Under the spotlight is Karl Muller, one of the first major enemies captured by the domestic intelligence agency in 1915, and his fruity demise. Agents suspected Muller of being a German spy but it was a humble lemon, on show in the "MI5: Official Secrets" exhibition, that brought him down. Muller claimed he used the fruit, found in his coat upon his arrest, to clean his teeth. But he had in fact used its juice as invisible ink on a seemingly ordinary letter intercepted by MI5, informing his...