1) An extraordinary number of informal lunchtime business meetings take place on the traffic island, outside the Royal Exchange, at Bank Junction.
2) Toilets that don't require payment to use are few and far between.
3) Sources of drinking water are equally hard to come by. You need to start collecting empty water bottles from the trash so that you can store a supply.
4) Even in the summer it gets cold at night. If you get cold then it's very difficult to get warm again. Pick up the free newspapers outside railway stations and use them to stuff your clothes.
5) A sheet of cardboard makes an incredible difference as an insulator and as a cushion between you and whatever hard and uncomfortable surface you happen to be sleeping on. You can pull a collapsed box out of the recycling bundles that the shops put out on the kerb, or you grab one from the cages outside the supermarkets.
6) If you place your ear to the ground in certain parts of London you will hear the sound of the tube trains passing by underneath. Sometimes you will also hear the platform announcements.
7) Your teeth and the inside of your mouth will be the first thing to go
8) After two days without food you will completely lose your appetite.
9) As you lose weight your trousers will slip down and begin to chaff. Make sure that you secure them properly around your waist or you will lose all the skin on your inner thighs and they will stick together when you walk.
10) Parts of London that are populated and generally safe during the day become less so after the crowds depart – e.g. the South Bank, along by The National Theatre.
11) Your biggest human threat is other homeless people. You will be a source of entertainment for drunken arseholes. Everybody else will ignore you.
12) You will win most confrontations by standing your ground and not being afraid to hit back if necessary.
13) The old city of London is generally safe at night but it's harder to find places to sleep that are out of the line of sight.
14) London is a big place. If you don't want to be found, you will not be found.
15) You will never see the places where you slept rough in quite the same way again.