Folk memories of great events often seem much rosier to people who didn't live through them. Films and pictures of the 1951 Festival of Britain, held on the south bank of the Thames in the last months of the Labour government's strangled second term, look beautiful and noble to someone who has experienced only the Millennium Dome. At the time, any public figure sceptical of its mastermind, Herbert Morrison, was keen to denounce it as a top-down socialist folly; despite that, half the population took part in celebrations throughout the country.
Morrison, the Labour deputy prime minister (and, for all his efforts, about as popular as his present-day counterpart), wanted "to do something jolly" for a war-battered population and landscape: "We need something to give Britain a lift." And so we did. David Kynaston's absorbing new book, Austerity Britain (1945-1951), shows us the history of that eventful half-decade through the eyes of Mass Observation diarists, one of whom, the schoolteacher Gladys Langford, reported visiting the Festival of Britain site shortly before it opened. "What a muddle!" she wrote. "Hideous buildings in a sea of mud!"
Despite the mess of the muddy embankment, she can't have failed to notice rising from it the festival's "lasting monument", as another his torian, Peter Hennessy, calls the Royal Festival Hall. Built in a single year at a cost of £1m - one-tenth of the cost of the whole Festival of Britain, which incorporated exhibitions on architecture and science as well as the celebrated Skylon sculpture - the hall has not only survived, but flourished as one of the few British modernist buildings that people actually like.
Two years after it was closed and swathed in scaffolding, it is about to reopen, following a £91m refurbishment programme that has restored many of the hall's original external features, thrown out of joint by brutal (and brutalist) extensions carried out in the mid-1960s. The hall has been lovingly returned to its old glory, but not in a spirit of shallow retro fetishism. With the project under the direction of the architects Allies and Morrison and Jude Kelly, artistic director of the rebranded "Southbank Centre", the bright, playful humanism of the hall's design has once again been made its strength.
This is because the Festival Hall was designed with progress and democracy at its heart: not as wishful concepts detached from the very people who would use it, but as a blueprint for a better future. In his own history of the 1945-51 period, Never Again, Hennessy quotes a young Michael Frayn naming the men behind the hall and the attendant festival "the Herbivores" - thoughtful (if paternalistic) creatures, doomed soon to be overtaken by the rugged capitalists he called "the Carnivores". "With the exception of Herbert Morrison," wrote Frayn back in the 1950s, "there was almost no one of working-class background concerned in planning the festival, and nothing about the results to suggest that the working classes were anything more than the lovably human but essentially inert objects of benevolent administration."
The Festival Hall was, perhaps because of its longevity, a different matter: there was nothing condescending about its graceful design. Its architects - Leslie Martin, Robert Matthew and Peter Moro from London County Council's architecture department - were influenced more by the Scandinavian approach to modern design than by Le Corbusier's scorched-earth method. Martin, who led the team, envisaged the hall's auditorium as an egg suspended in its box, cushioned from the rumbling of the nearby railway bridge, and immune to the sounds of traffic and Festival-going.
Originally visitors could approach and enter the Festival Hall from any angle, giving a sense that anyone could gain access to it at any time; but its main point of entry has long since flipped from south to north, from unfashionable Lambeth to raffish Bankside, in full sight of the West End. Allies and Morrison have swapped it back, so that the hall looks out to south London and no longer seems to snub it. The new entrance opens on to a public square and is framed by a branch of the trendy comfort-food chain Canteen.
Inside, the People's Palace restaurant is being replaced with a new top-notch Conran franchise, Skylon. This is one area where the dem ocratising intentions of Kelly and her team go slightly awry. Canteen sells pies and kidneys with mash at £9 or £10 a throw: cheap by London standards, but still hardly greasy-spoon prices. I don't yet know what Skylon will charge, but it won't be buttons. Much of the space surrounding the Festival Hall has been opened up into a sort of outdoor food court: there's a Ping Pong dim sum bar, a branch of the gorgeous Belgian bakery/cafe Le Pain Quotidien, a Strada pizza place and a Wagamama noodle bar. It has provided Southbank coffers with a crucial source of revenue and turned a former food desert into a cornucopia: at least, if you can afford it and you don't think it's poncey.
Similarly, the hall's roof terraces, designed to give visitors one of the loveliest views in London but which have long been given over to extra office space (the Southbank staff now have offices across the way), have been cleared, fitted with panoramic glass windows - and set aside as a corporate entertainment area. You will be able to visit the terraces and marvel at the sweeping view from the London Eye across the river to Big Ben, but only when the prawn sandwich brigade is not around. Though these ventures will undoubtedly help to pay for activities of the RFH's vastly expanded education centre in the basement - named the Spirit Level by Kelly - they prove that it's not quite the hall for all.
But these are gripes. The huge quantities of detail that made the Royal Festival Hall one of Londoners' favourite buildings have been polished up and restored as sustainably as possible. Peter Moro's "net and ball" carpet, produced by Wilton's, has been completely rewoven (a chunk of the old one has found its way on to the floor of the RFH artist-in-residence, Bob Stanley of the band Saint Étienne) and his original colour scheme reinstated many years after some dull types painted every wall white.
Most of the work in the auditorium has been carried out to improve and support its acoustics, which have been overhauled by the American acoustician Larry Kierkegaard. There is now an elegant series of sail-like, moveable white panels above the stage, and the excess woodblocks that were removed from the auditorium floor to increase the size of the stage have been recycled as sound-bouncing panels along the side walls. Robin Day's seats have been reupholstered and given individual dedications as part of a "sponsor a seat" fundraising campaign. The hall feels bigger and brighter, and invites you to sweep through it without the interference of pillars or filled-in bits. You can see straight through the ground level from one glass wall to the other. Now that there are fewer visual or physical impediments to entering the building, and to feeling free once you're inside it, Kelly's remaining challenge is to get people through the invisible doors in the first place.
The launch event for the reopening of the hall is the "Overture Weekend", comprising 48 hours of free music from Friday 8 June to Sunday 10 June. For the 11 June gala first night, the RFH's four resident orchestras - the London Philharmonic Orchestra, the Philharmonia, the London Sinfonietta and the Orchestra of the Age of Enlightenment - will gather on stage to perform work by nine composers, including Ravel's Bolero. Coupled with my vision of every worker doing half-days and spending the afternoons reading Plato in the park, it is an uncanny representation, in my head, of the socialist paradise.
"When the Festival Hall reopens, we want it to embody the hopes and dreams of the people who created the site," Kelly told London's Time Out magazine in February. "They spoke bravely about the future - it's up to us to do the same." Speaking bravely about the future requires asking whether a building of this type, and the events it holds, can ever be truly accessible to all while inequality strips so many of entitlement and public buildings are forced to hive off their highlights in order to generate revenue.
Those in charge of renovating the Royal Festival Hall have reminded us that it is worth doing something well: it makes us less cynical, and it restores our faith that there are people who care about how buildings look and feel, down to the last detail. More importantly, let's hope this example is one that others elsewhere will follow.
The refurbished Royal Festival Hall opens to the public on 11 June. For more information on the RFH celebrations, log on to: http://www.southbankcentre.co.uk