Visitors to that hub of our parliamentary democracy, the central lobby of the Palace of Westminster, can see at once that they are in the presence of two essential pillars of the British constitution. Looking to the right, through the multicoloured tunnel of the House of Lords, the visitor can see the throne in all its golden magnificence. Looking to the left, at the other end of the long vista, he can see the Speaker's chair. They are the visible evidence of the Queen in parliament, supposedly the centrepiece of our system of government.
Few visitors can fail to be interested, if not actually excited, by such a piece of symbolism. But it is highly unlikely that more than a handful of them will realise that immediately beneath their feet is a third, less formal pillar of the British constitution. It is called Annie's Bar, and it is no ordinary watering hole. For many years it was the exchange and mart of the political trade.
It isn't an easy place for a stranger to find, even if he were permitted to enter it. But just for the record, if you treat the public entrance to the lobby from St Stephen's Chapel as six o'clock, at 11 o'clock you will see a dusty-looking glass door hidden behind a large bench. On the other side is a stark concrete stairway which curves downwards. At the bottom are a number of plain wooden doors. One of them opens into Annie's Bar.
Inside is a windowless cell which would be claustrophobic if it were not dressed up to look like a more-or-less comfortable bar. It used to be the policemen's pub and was known by the name of its barmaid, Rosie. Rosie was notoriously deaf, but miraculously recovered her hearing if you said, "What'll you have, Rosie?"
Nowadays its occupants will be journalists, MPs, one or two junior ministers and a few officials of the House. No outsiders are admitted, and it is the only bar in the Commons where these three groups can meet on entirely equal terms. In all the other watering places - and there are many - one or other group must be invited as a guest without the right to buy a drink.
It is this apparently trivial rule which makes Annie's Bar so valuable to the process of disseminating news. It is the place where talkative MPs can go, safe in the knowledge that, whoever they meet, they will not have to pay for all - or possibly any - of the rounds that come up. It is equally the place where a minister with something he wants to leak can be sure of finding a receptive audience. It is also the place where the whips of both parties can exchange gossip with reporters, to their mutual profit.
The origin of Annie's Bar is obscure, but it is certain that just such a bar existed for many years before the second world war, up until the moment when the Commons was wrecked by German bombs. In those days it occupied a tiny cupboard-like room which opened directly on to the members' lobby. Like Rosie's, it acquired its name because the barmaid was called Annie.
Its main drawback from the point of view of its customers was that it had no running water, so hygiene depended on a bucket behind the bar. By the end of a hard day's legislation, the liquid in this receptacle could scarcely be distinguished from the beer in the barrel beside it. As a result, the more fastidious drinkers tended to go for spirits, if only because of their antiseptic qualities.
But from the point of view of the Labour whips, there was another serious drawback. One of the party's elder statesmen, Arthur Greenwood, had a well-known weakness for whisky, and he came to spend a great deal of time in Annie's, gossiping with journalists who were only too willing to supply the necessary lubricant. It wasn't just the danger of unauthorised leaks that worried the whips; it was that "Uncle Arthur" was sometimes a tiny bit fuddled when he took his place on the front bench.
The direct result of this was that, when the chamber was rebuilt after the war, there was no Annie's Bar. Attlee's chief whip, a stern teetotaller called William Whiteley, was determined that boozy journalists would not have the opportunity to rot the moral fibre of his ministerial colleagues. The little taproom became an office for the opposition whips, and Annie herself was retired. The only reminder of its existence is a gothic inscription carved round the wall of the members' lobby which appears to say "Saloon Bar" just over the doorway.
Whiteley must have been disappointed by the effectiveness of his ban, since we reporters still found ways of pouring drink into Labour MPs and ministers. But his ban survived for fully 20 years, in spite of constant agitation from lobby correspondents for a new Annie's. What changed the situation was the appointment of the Labour MP for Buckingham as chairman of the Commons catering committee.
This individual was none other than that old crook Robert Maxwell, alias Cap'n Bob, later to be proprietor of the Daily Mirror. At this stage in his career he was just a minor crook, and he secured the job by promising gullible MPs that he would bring the loss-making department into profit within a year. His first step towards achieving his ambitious target was to close down all the cafeterias and restaurants in the Commons from 9pm, replacing them with American-style slot machines containing ready frozen-meals, which you defrosted for yourself in a microwave oven.
His next act of vandalism was to sell off the contents of the incomparable House of Commons wine cellar at knock-down prices (you could buy a glass of Chateau La Tour over the bar for 30p) and to let out the vacated space to a big retail vintners. But he spotted an opportunity to build up Brownie points with the press, and announced that he would be reopening Annie's.
Annie's Bar Mark II was established in a ground-floor room under the tea room. It had formerly been a rest room for female catering staff, and you could see the burns on the exquisite oak panelling where they had boiled their kettle. Further research revealed that it had once been Parnell's room, raising the scurrilous thought that he might have "entertained" Kitty O'Shea there from time to time.
The new bar was opened by Ted Heath, then leader of the opposition, and the first pint was drawn by Annie herself, who had been brought back for the occasion by the publicity-conscious Cap'n Bob. He had not miscalculated. He became an overnight hero with lobby journalists, getting surprisingly gentle treatment even when it turned out that he had fulfilled his promise to get the catering committee into the black by the simple expedient of not paying the bills.
This came to light only when Maxwell lost his seat in 1970, and a new chairman opened the books. But like Maxwell's fatal yacht, Annie's sailed on without Cap'n Bob. It had already become a vital marketplace between press and politicians during the crisis over Barbara Castle's plan to curb trade union power. It became even more valuable during the Heath years, punctuated by miners' strikes and the ludicrous three-day week; it acquired its ultimate status as an essential pillar of the constitution during the 1974-79 Labour government, a roller-coaster ride which included the fall of Heath and the triumph of Thatcher.
With no government majority, every Commons division became a cliffhanger which had to be monitored. The monitoring was most effectively done from Annie's, just one flight of stairs from the members' lobby. One could gauge the degree of crisis every night by how often the whips scuttled in and out in search of missing MPs.
Nor did the frenetic atmosphere change when the Blessed Margaret began her endless reign. Annie's was the place where the so-called "wets" came to bemoan their suffering under Mrs T's lash. It was also the place where Reggie Maudling, the one-time leadership hope of the Tory left, wept into his whisky as he awaited the verdict of the Commons on his dodgy dealings with a corrupt architect. And it was the place where the loony left of the Labour Party came to reveal their latest lunacy to an attentive press.
True, there were those who stood aside from this booze-fuelled traffic. Tony Benn, a lifelong teetotaller, never entered the place. Nor did Dennis Skinner, who objected to taking hospitality from the capitalist press. He solved the problem of how to communicate by hanging about in the corridor and sending in messages that he was waiting outside.
But a succession of chief whips from both parties were regulars, and their deputies even more so. Even Roy Jenkins came in once, dragged there for PR purposes by his political aide. He didn't like it, and never came again. Thatcher came as a shadow minister, but always as a guest. Successive Speakers were regulars before they were elected to the chair, and at least one tried to continue drinking there until he was warned off by senior MPs.
I suspect that such goings-on do not appeal to Tony Blair, or fit the buttoned-up image of new Labour. It reeks of old Labour and old Tory. Too many careers were wrecked there, and at least one former foreign secretary fell off his bar stool quite frequently while he drowned his sorrows in gin and french.
The recent move from Kitty O'Shea's love nest to the windowless cellar under the central lobby has not helped matters, either. It is less accessible, and some new members are probably too fearful of the whips even to ask where it is. Add to that a curious tendency among the once notoriously boozy press to eschew strong drink - perhaps they have to keep sober for the sake of their computers - and it wouldn't be surprising if Annie's were to go into terminal decline. After all, some people believe that parliament itself is in terminal decline.
So the odds are that Alastair Campbell, Downing Street's non-drinking press secretary, would not be at all displeased if this dangerous source of unauthorised leaks were to be shut down for a second time. Indeed, he may even have drafted the appropriate words for next year's Queen's Speech. I can almost hear them now: "Members of the House of Commons, as a constituent part of my government's programme of radical constitutional reform, a measure will be placed before you to abolish Annie's Bar."
What's more, I bet there won't be anything to take its place, either. Like a Freedom of Information Bill.