Comedian Paul Coulter, whose show 5 Mistakes That Changed History tours the UK this summer, identifies five of London's most forehead-slapping eff-ups.

London, with its higgledy piggledy streets, is the definition of somewhere built by trial and error. Many, many errors. Mistakes are part of what makes our city great. But looking back on them, they're also bloody embarrassing. Nonetheless, here goes...
Leaving the gates open
The Tower of London. Impenetrable. Except for this one time. The year was 1381. The peasants were revolting. And someone had forgotten to shut the gates while the King was out negotiating with the rebels. Oops. Spotting their chance, the Tower was seized by the rebels, the Chancellor dragged out and beheaded. The swordsman made at least seven mistakes of his own... it took eight painful swipes to lop off the Chancellor's head. The sword also took off some fingers for good measure.

Forgetting to check the oven
Perhaps the most infamous of all London's mistakes, the Great Fire of London gutted the medieval heart of the city, and destroyed the original St Paul's. It was sparked, infamously, by a fire not properly extinguished by the King's baker, Thomas Farriner. 17th century firefighting left a lot to be desired and the rest is history. The Monument to the Great Fire of London still stands near the site where the blaze broke out — a call to all Londoners to remember if they've turned the oven off.

Decapitating the King
A bit awkward this one, but we chopped off our own King's head. Unlike the French (for whom chopping up royals was a national pastime) we're still ever so embarrassed about it. We even sewed his head back on before burying him! Royalty was restored in 1660, and Parliament has been profusely apologising for briefly losing its (and the monarch's) head ever since. We're on our third King Charles now, and will forgive him for steering clear of Parliament whenever he can...

Drinking lethal water
In 1854, a catastrophic cholera epidemic raged through London. Terrified Victorian Londoners were convinced the outbreak was caused by 'bad air', some fleeing the city. But calm and collected physician John Snow tracked the outbreak down to a single water pump in Soho. He proved its supply was contaminated by dirty nappy water — Evian this was not! Snow's discovery not only saved London but also launched the science of modern epidemiology. Today a replica of the pump reminds us of the episode, though if you're feeling thirsty, I'd recommend the John Snow pub, opposite.
Building a wobbly bridge
The Millennium Bridge had an unsteady start, quite literally. Immortalised in Harry Potter, when it was wrecked by dementors, the bridge actually proved pretty bloody wobbly when it opened in real life, back in 2000. Summoning up all its collective wit, the press nicknamed it the 'Wobbly Bridge', and the pedestrian crossing quickly closed down for 20 more months of engineering works. (Nothing really says London like 'engineering works'.) Still, all publicity is good publicity, right.
Parisians can keep their grand avenues, and New Yorkers, their clinical grid system. London is the most human of cities; its madcap nature shaped — much like our own lives — by mistakes. Because sometimes you can't plan 'great'. It happens not by design, but by accident.
Paul Coulter's comedy show 5 Mistakes That Changed History, is on tour across the UK this summer, including at the Edinburgh Fringe.