‘The way to avoid being mugged,’ my dad said, ‘is to look as if you’re going to mug someone.’ Memorable advice – well, I’ve remembered it, which is more than I can say about most of what he told me before I went to London. What made it stick was the thought it immediately prompted in me: that I could never, ever imagine my dad looking as if he were going to mug someone. This gem of street-smarts was dispensed by a diminutive, paunchy tax accountant wearing an incredibly aged blue blazer with loose brass buttons that dangled like charms on a bracelet. When my dad started losing his hair, it went at the temples first, as is quite common. But then it kept going back in two temple-width swaths, never expanding its path to take in anything from the sides or the top of the head. This left a mohican-like strip of hair in the middle of his scalp. He never did anything to adapt his hairstyle to the diminishing resources at its disposal, to try to disguise or balance the creeping baldness – a failure I saw then as a hopeless inability to face facts but in retrospect looked more like splendid unconcern. He simply did not mind.

Did he, my dad, base this advice on experience? Or was it just something he had heard and which sounded true enough to repeat without checking? So much ‘wisdom’ is like that, plausible but untested, repeated with confidence because it had been heard spoken with confidence. What did it even mean, in practice? A scowl on the face, a certain swagger, a certain swing, a certain strut to the walk. To appear at home in the street, as if you belong wherever it is that you are, which may be – if violence really is a possibility – what the newspapers call ‘the wrong place at the wrong time’. There’s data for you: if places and times can be ‘wrong’, then there are temporal and topological boundaries, this could all be mapped – indeed, apps like Tamesis could show you recent crime as a heat map. I knew because I hate-browsed homes for sale on those apps, seeking out the pockets where public-transport access was chilliest and crime was glowing magma red, hopeful of a miraculous, inaccessible few streets of nightly throat-slitting where a studio flat might dip towards a quarter of a mill.

You mustn’t look out of place, you mustn’t look like an impostor. That’s when the city turns on you. But it’s not quite right to say you must appear ‘at home’. Because when you’re drunk you often feel supremely at home on the street, altogether too comfortable, and you’re at your most vulnerable.