Mine involves my first and only run-in with the police.
A few years back, I was in a non chain pizzeria near Old Street with two friends. I'd just taken a bite off my second piece of pizza when I realised I was chewing what can only be described as a knot of black hair. I discreetly told the person serving our table, who also transpired to be the restaurant manager. I was disgusted, but very polite - almost embarrassed to have to ask for it to be taken back.
He was not happy: he did not believe about the hair(s), and when I fished the evidence out of the serviette, he accused me of pulling my own hair and putting it the food in order to get free pizza! He even called the chef out of the kitchen to show me that he was bald, ergo the hair must have been mine! All this in a very loud voice and causing a real scene in front of the other customers.
At this point my friends got really angry on my behalf (I was just sitting there speechless), threw a tenner on the table for their food and stood up to leave. Manager shouted that I should too pay for my pizza and, when we refused, he called us thieves and started all sorts of insults and threats. My friends were shouting back and before we knew it, the bald chef had called the police!!!
I don't think I've ever been in a more ridiculous situation in my life than when the policemen asked me for my testimony.
In the end, the police just instructed the guy to let us go without paying for my pizza since it had not been sold to me as advertised, i.e. sans hair.