Although largely informal in their everyday dealings, Londoners do observe some (unspoken) rules of etiquette.
Strangers Unless asking for directions, British people generally won't start a conversation at bus stops or on tube platforms. More latitude is given to non-British people.
Greetings When meeting someone formally for the first time, shake hands.
Queues The British don't tolerate queue jumping. Any attempt to do so will receive tutting and protest.
Tube Stand on the right and pass on the left while riding an Underground escalator.
Bargaining Haggling over the price of goods (but not food) is OK in markets, but non-existent in shops.
Punctuality It's not good form to turn up more than 10 minutes late for drinks or dinner. If you're unavoidably late, keep everyone in the loop.
Apologise The British love apologising. If you bump into someone on the tube, say sorry; they may apologise back, even if you are to blame.