For a large number of the population, pantomime is their only contact with live theatre. For some, it is a family visit. Others attend in coach parties - many of which are school outings. The number of regional theatres which still stage January matinees at 10.30am or 1.30pm suggests that many schools still organise a pre- or post-Christmas trip to the local panto.
This continuing popularity means that many provincial theatres that usually rely on touring shows still stage a home-grown production once a year. On the other side of the curtain, children get an unbridled opportunity not only to boo, hiss and cheer, but to participate in a traditional form of entertainment.
In view of its popularity and accessibility, it is easy to be supercilious about panto, or to claim that it isn't what it used to be. Many deplore its "emasculation", pointing to productions that have made villains less frightening, banished witches and cut the blue jokes - and to one "politically correct" company that retitled its show Snow White and the Seven Persons of Different Stature. Then there are those who lament the reliance on jokes about TV and politics, and the proliferation of pop, sport and soap stars in the casts. But the same complaints were being made in 1879 when music hall stars first made their entrance on the panto stage.
Many producers do now rely heavily on soap stars to attract punters. This year, at least 15 current and former members of the EastEnders cast are donning fishnet tights or transforming themselves into fairy godmothers. "Phil Mitchell" (Steve McFadden) is doing it in Milton Keynes, "Laura Beale" (Hannah Waterman) in Dartford. Cast members from Australian soaps, Coronation Street, Emmerdale, Brookside and even Crossroads get star billing. So, too, do names from situation comedies now seen only on UK Gold. And presenters of Blue Peter and The Sooty Show, "H" (once in the band Steps) and Shane Lynch of Boyzone are also booked to widen panto's appeal. The latest trend is to include so-called stars of reality shows. Winners of Channel 4's Big Brother are suddenly deemed to have enough acting talent to star in Aberdeen, Southampton and Southport.
Despite seeming to be set in stone, panto has always been a developing format. Its roots lie in the 16th and 17th-century Italian improvised comedies known as commedia dell'arte, in which the same stock characters appeared in each production, acting out predictable storylines, rather like the weekly episodes of a long-running sitcom. This genre ws brought to London in the early 18th century by French fairground performers.
Imitations soon appeared in Drury Lane and Haymarket, the first half of the show taking the form of a classical myth, the second being a knockabout "harlequinade".
Gradually, the classic scenes were replaced by folk tales, retold by the French writer Charles Perrault in his 1697 collection, Mother Goose's Fairy Tales. These included "Puss-in-Boots", "Cinderella" and "Red Riding Hood".
By the 19th century, the two halves of the entertainment had combined to form something recognisably like modern pantomime.
By this time, the "dame" role was being played by a man, Harlequin was wearing his skintight, lozenge-patterned suit and the shows were being presented chiefly at Christmas and Easter. In 1806, the famous clown and acrobat, Joseph Grimaldi, appeared as Clown in Mother Goose at Drury Lane.
It was a defining moment: not only was he from outside "legitimate" theatre (and therefore the ancestor of all non-actor participants), he introduced and led community singing. From then on, much of the comic business of panto was focused on the Clown rather than Harlequin.
During the Victorian era, productions became ever more elaborate, with gas lighting, fire and even gunpowder being used for spectacular transformation scenes. This could involve numerous gas jets, connected to various parts of the scenery by rubber tubing which had to be installed, adjusted and hastily removed (twice nightly). As the scenery consisted entirely of wood and canvas and the backstage area was crowded with dancers clad in gauze and muslin, one can only marvel that there were not more fires.
During this period, pantomimes were increasingly devised to please children and it was therefore predictable that when "adult" jokes and music-hall stars such as Marie Lloyd, Vesta Tilley and Dan Leno appeared, there were public complaints. Leno was a small man with a sad but expressive face, described by Charlie Chaplin as "the greatest comedian since Grimaldi". He had been the champion clog dancer of England before carving a niche for himself as a Dame.
After the First World War, panto began to disappear from London's West End but enjoyed an enduring popularity elsewhere. Audience participation devices, such as "oh-yes-it-is, oh-no-it-isn't" and "look, he's behind you", the invitation to children to come up on stage and the final sing-along, became established. So too did the tradition of involving troupes from local dance schools.
Other changes have been the casting of a man as Principal Boy, a fashion that began in 1961 but was broken when Cilla Black reclaimed the role in 1971. The role of Dame, which remained obviously a man (Les Dawson-style), began to be taken by drag queens who dressed not in voluminous petticoats but in glamorous gowns. These Dames are not always involved in slapstick scenes: it's not a good idea to cover a glittering evening dress with wallpaper paste or custard.
In the only two pantos to be seen in central London this year, the Dame in Snow White at the Victoria Palace is Lily Savage (Paul O'Grady) while the Old Vic has cast Ian McKellen as Widow Twankey - presumably because of his fame as Gandalf rather than for his Shakespearean pedigree.
Aladdin seems to be especially popular this year after a period out of fashion, possibly because it traditionally relied on stereotypical Chinese jokes. Other popular productions are Jack and the Beanstalk, Sleeping Beauty, Dick Whittington, and the all-time favourite, Cinderella. Mother Goose and The Babes in the Wood are staged less frequently because of their comparatively slight plots. The latter often resorted to the inclusion of such characters as Robin Hood, Maid Marian and even Titania, Queen of the Fairies, to flesh out its storyline.
A detailed "script" is a comparatively recent innovation. Roy Hudd recalled his first experience of panto in 1960. At the first rehearsal, the "read through" took well under an hour. The typescript was punctuated by pages that were blank except for phrases such as "Ghost Gag here", "Spesh act" (speciality act) and "Front of cloth routine" (where two comedians would exchange jokes in front of the curtain while the scenery was changed).
Nowadays, the technical complexities of lighting, sound and special effects demand a detailed script that may be written by the comedians in the cast.
Even so, there will be variations each night as characters ad-lib their way around audience reactions.
This is part of panto's lasting appeal: no two performances are the same.
Added to that is its unique mixture of comedy, dance, song, transformation scenes, elaborate costumes and spectacle. Authority is mocked and roles reversed (echoes perhaps of medieval Christmas customs such as the installation of "boy bishops" for the 12 days of Christmas, masters waiting on servants and the licence encouraged by Twelfth Night Lords of Misrule).
There is also the certainty that true love will triumph. But possibly even more important than all this is the fact that pantomime is the one form of theatre which actively encourages audience participation: in it, we are all performers.