Invisible ink failed to fool the British Secret Service during the First World War. And as spying during World War I was punishable by death, Carl Friedrick Muller felt the full force of British wrath after he was executed for his betrayals. Yet he almost missed his own execution after the black cab broke down on its way to the Tower of London.
For Muller had stood charged with ‘feloniously attempting to communicate and recording and collecting information with respect to military and naval forces and war materials with intention of assisting [the] enemy’ – to you and me that means passing armed forces’ secrets to the opposition. And the opposition meant Germany.
He’d been enlisted as a secret agent by the Germans, not least because he could speak a number of languages fluently. He was in shipping and was hard up – the perfect combination.
As a result, Muller was to travel between Germany and Britain seemingly innocently, writing correspondence detailing shipping movements to his German pals – but little did he know the Brits were on to him and had intercepted his letters.
Unsuspectingly, in February of 1915, he hooked up with a Brit (of German extraction) – John Hahn, who was an East-end baker and together they sent more incriminating letters. Both were unaware their illicit communications were being diverted to Special Branch for closer inspection.
There CID found secret German messages written in formalin (formaldehyde) and lemon juice in between what appeared to be innocent letters written in English. The two were busted.
Both men were hauled in and while Hahn pleaded guilty and got seven years, Muller pleaded not guilty and got death. The latter was housed at Brixton Prison and on the day of his execution, he was taken by black cab to the Tower of London where he was to be executed. According to Stephen Stratford it broke down, so another took him on to the place of execution.
So Muller was riddled with a slew of bullets on this day within the grounds of the Tower of London in 1915.
According to a couple of sources, New Scotland Yard’s Assistant Commissioner of Police, Sir Basil Thomson witnessed the execution by firing squad. It was carried out by eight soldiers. He observed: ‘I saw no expression of pain. I found no pulse and no sign of life. Death appeared to be instantaneous, and the body retained the same position. The bullets probably in fragments had passed through the thorax and out of the back. Some blood, mixed with what appeared to be bone, had escaped through the clothing…’. And with that, the second spy to be executed during World War I was pronounced dead.
Details of Muller’s trial and evidence of his damning correspondence now sit in The National Archives at Kew.