You may remember the high jinks I had when I set my mate Andy on fire. This further cautionary tale of pyrotechnical idiocy, from my long delayed autobiography, doesn’t involve me, because even I’m not this stupid.

A little scientific background. If you didn’t do chemistry at school, you may not be aware of the reactivity of the alkali metals that form Group 1 in the periodic table. Lithium, sodium, and potassium will react with water, and potassium is a right little tinker in this respect. Drop a bit the size of a match head in a large quantity of water, and it zips around because it’s producing hydrogen from the water so it’s like a diddy hovercraft. The reaction is strongly exothermic too, so the hydrogen actually ignites, and you get the pretty lilac flame associated with potassium.

The alkali metals are so bloody reactive you have to store them in oil so water can’t get at them. At my school the storage containers were squat glass bottles with narrow necks and glass stoppers. Some hoodlum decided it would be a wizard wheeze to hoy a bottle of potassium down a toilet. He figured he could get clear before the oil floated off the contents and there was a bang.

Sad to relate, it didn’t quite go to plan, and the potassium detonated almost instantaneously. How he didn’t die in the resulting firestorm is anybody’s guess, but he did live to tell the tale, albeit with eyebrows that took a while to grow back, and some minor damage sustained to his blazer. Took a bit for his hearing to recover too.

The toilet itself was made of stern stuff, as it needed to be to handle the bowel movements of adolescent boys, and while the seat was mildly scorched the rest stood majestically intact.

At the point where the perpetrator was still staggering about smouldering and moaning like a zombie in a B movie finale, our revered deputy headmaster appeared hot foot, having been alerted to the malfeasance by the very impressive explosion.

‘Has anybody seen a bang?’ he asked.