As well as preventing carnage and mayhem, round-buying is also vitally important because it is an Englishman's substitute for the expression of emotion. The average English male is terrified of intimacy, but he is also human, and therefore has a need to bond with other humans, particularly with other males. This means finding some way of saying 'I like you' to other males, without, of course, actually having to utter anything quite so soppy. Fortunately, such positive feelings can be expressed, without any loss of masculine dignity, by the reciprocal buying of rounds of drinks.
The importance we attach to round-buying is also yet another indicator of our obsession with fair play - round-buying, like queuing, is all about taking turns. But, like every aspect of English etiquette, the unwritten rules of round-buying are complicated, with all the usual sub-clauses and exceptions, and 'fairness' is a somewhat slippery concept - it is not just a simple matter of ensuring roughly equal expenditure on drinks. The rules of round-buying are as follows:
* In any group of two or more people, one person must buy a 'round' of drinks for the whole group. This is not an altruistic gesture: the expectation is that the other member or members of the group will each, in turn, buy a round of drinks. When each person has bought a round, the process begins again with the first person.
* Unless the group is drinking at the bar counter, the person who buys the round must also act as waiter. 'Buying your round' means not only paying for the drinks, but going to the bar, ordering the drinks and carrying them all back to the table. If there are a lot of drinks, another member of the group will usually offer to help, but this is not compulsory, and the round-buyer may have to make two or three trips. The effort involved is as important as the expenditure: it is part of the 'gift'.
* 'Fairness' in round-buying is not a matter of strict justice. One person may well end up buying two rounds during a 'session', while the other members of the group have only bought one round each. Over several 'sessions', rough equality is usually achieved, but it is extremely bad manners to appear overly concerned about this.
* In fact, any sign of miserliness, calculation or reluctance to participate wholeheartedly in the ritual is severely frowned upon. For an English male, saying that someone 'doesn't buy his round' is a dire insult. It is thus important to try always to be among the earliest to say 'It's my round,' rather than waiting until the other members of the group have bought 'their' rounds and it is quite obviously your turn.
* Perhaps surprisingly, I found that on average 'initiating' round-buyers (those who regularly buy the first round) actually spend no more money in the long term than 'waiting' round-buyers (those who do not offer a round until later in the session). In fact, far from being out-of-pocket, 'initiators' often end up rather better off than those who wait, because their popularity and reputation for generosity means that others are inclined to be generous towards them.
* One should never wait until all one's companions' glasses are empty before offering to buy the next round. The correct time to say 'It's my round' is when the majority of the glasses are about three-quarters empty. This rule is not so much about proving one's generosity, more a matter of ensuring that the flow of alcohol is continuous - that no-one is ever left without a drink for even a few minutes.
* It is acceptable occasionally to refuse a drink during the round-buying process, as long as you do not attempt to make an issue or a moral virtue out of your moderate intake, but this does not exempt you from the round-buying obligation. Even if you are drinking less than the others, you should still 'buy your round'. It would be very rude, however, to refuse a drink that is offered as a 'peace-making' gesture, or that is clearly a significant, personal friendship-signal.
There is usually no excuse for failing to perform the sacred round-buying ritual, but there are a few exceptions to the round-buying rules, relating to the size of the drinking group and the demographics of its members.
THE NUMBERS EXCEPTION In a very large group, traditional round-buying can sometimes be prohibitively expensive. This is not, however, usually seen as a valid reason to abandon the ritual altogether. Instead, the large group divides into smaller sub-groups (nobody suggests or organizes this, it just happens), each of which follows the normal round-buying procedure. Alternatively, the principle of gift-giving is maintained by having a 'whip round' - collecting a relatively small sum of money from each person to put into a 'kitty', which is then used to buy rounds of drinks for the whole group. Only as a last resort, perhaps among students or others on very low incomes, will members of a large group agree to purchase drinks individually.
THE COUPLE EXCEPTION In some social groups, couples are treated as one person for the purposes of round-buying, in that only the male half of the couple is expected to 'buy his round'. This variation is rarely seen among younger people, unless they are deliberately adopting old-fashioned courtly manners for some special occasion. In normal circumstances, you will only see this practice when the males in the group are over forty. Some older English males cannot cope with the idea of women buying them drinks at all, and extend the couple exception to cover all females in a group, whether or not they are accompanied by an attached male. When out alone with a female, these older, old-fashioned males will also insist on buying all the drinks, whereas younger males will usually expect a female companion to take turns buying rounds in the usual manner.
THE FEMALE EXCEPTION Women generally have considerably less reverence for the round-buying rules than men. In mixed-sex groups, they play along, humouring their male companions by following the prescribed etiquette, but in all-female gatherings you see all sorts of odd variations and even outright flouting of the rules. They do buy each other drinks, but round-buying is just not such a big issue for them - they don't keep track of whose round it is, or have endless friendly disputes about who has or hasn't bought their round, and they tend to find the male obsession with round-buying somewhat tedious and irritating.
This is mainly because English females have much less need for the 'liquid handshake' of reciprocal drink-buying than English males: the argument is not their primary form of communication, so there is no need for peacekeeping gestures, and they are quite capable of conveying that they like each other and achieving intimacy by other means, such as compliments, gossip and reciprocal disclosure. English women may not be as free-and-easy with their disclosures as women from other, less inhibited cultures: they do not tend to tell you all about their divorce and their hysterectomy and what their therapist said within five minutes of meeting you. But once English females become friends, such discussions are commonplace, whereas most English males never get to this stage, even with their best and closest friends.
Even the word 'friend' is a bit difficult, a bit too touchy-feely, for some English males: they prefer to use the term 'mate'. You can be 'mates' with someone without necessarily knowing anything at all about his personal life, let alone his feelings, hopes or fears - except where these concern the performance of his football team or his car. The terms 'mate', 'good mate' and 'best mate' are ostensibly used to convey varying degrees of intimacy, but even your 'best mate' may know little or nothing about your marital problems - or only as much as can be conveyed in a jokey-blokey, mock-moaning manner, to which he can respond, 'Women! Huh! Typical!' You would, of course, risk your life for him, and he for you. Your 'best mate' may have a better idea of your golf handicap than the names of your children, but you actually care deeply about each other. Still, that goes without saying, right, so there's no need to cause unnecessary embarrassment by saying it. And anyway, it's your round, mate.