Wittgensteinʼs words to the wise were ʻdonʼt try and shit higher than your own arse.ʼ He was a prince among philosophers. He was also, take it from me, a spy. If the golden grandfather of philosophy skulked in the shades of espionage, does this compromise his morals or exonerate spying? Whatʼs the difference between a sleuth, a snoop and a snake?

In Britain we love to spy and be spied upon. Reality shows are novocain for the sharp pangs of our undercover yearnings. We cherish our mobile telephone numbers until they become our personal bar codes. National Express train posters encourage you to report fellow passengers who are propping their feet on the seat or hiding in the loo from the conductor. There is little irony in Big Brotherʼs Britain.

Yet Britain has a legacy of wonderful, witty spies and spy stories. Nevertheless, weare in danger of becoming a nation of spies. Even worse, we are in danger of becoming a nation of humourless spies. In an age of smart phones and CCTV letʼs not forget that when a country turns its peephole on itself, eyeballs begin popping. In Stasi Germany neighbours tinkered with listening devices in their watering cans. Odds-on you were related to your informer.

When spy culture turns into witch-hunt, when humour is drowned, Wittgenstein, who went to the same secondary school as Hitler, bangs on the lid of his coffin and hollers: ʻHumour is not a mood but a way of looking at the world. Humour was stamped out in Nazi Germany. That does not mean that people were not in good spirits, or anything of that sort, but something much deeper and more important.ʼ Chaplin, who was once accused of being a spy, although he never was, sent Hitler up in The Great Dictator because fear had created a vacuum of humour.

Good spies keep it light, bright and camp. James Bond is, of course, the king of kittenish one-liners: ʻnow put your clothes back on, and Iʼll buy you an ice cream.ʼ And we have Sherlock Holmes to thank for the delightfully suggestive ʻcome Watson, come! The game is afoot. Not a word! Into your clothes and come!ʼ Casanova was such an impish spy he tricked everyone into thinking he was an even better lover. If spies take themselves too seriously then no one else will. This is when we are unexpectedly assassinated as punishment for getting caught up in our own drama. Espionage may be no laughing matter, but life and death can depend upon the humorous twinkle in your eye because spies make and meet death as their meal ticket. There is great strength and endurance in humour. Wiser to fall down laughing than be brought down weeping.