Lord Melbourne, one of Queen Victoria's favourite prime ministers, once said: "God help the government that meddles with art." But since the end of the 19th century, the Government Art Collection, known to insiders as the GAC, has been acquiring paintings, sculpture and works in more heretical media with zeal. The outcome, an array of almost 12,000 images, remains one of Whitehall's best-kept secrets.
The aura of mystery is inevitable. Unlike the National Gallery, whose collection is only a fifth of the size, the GAC bestows its treasures on spaces with limited public access. No fewer than 150 government buildings in Britain, as well as 300 resi-dencies and embassies abroad, are able to display work. The idea is "to promote British art and culture across diverse and international environments". But the GAC itself, discreetly housed near Tottenham Court Road in central London, is not equipped to cope with the prodigious visitor numbers attracted by, say, the Tate.
On the fourth floor, where the director, Penny Johnson, has her office, a display area offers a taste of the collection's surprising range. On one wall, Mark Wallinger's blank-faced jockeys look stunned after returning from the gilded opulence of the British ambassador's residence in Paris. Alex Hartley's blurred interior in satin-etched glass juts out provocatively from another wall. Positioned at the end of a corridor, it is an imaginative commission that testifies to Johnson's open-minded involvement with contemporary British art.
She took over from Wendy Baron in April 1997. "It was three weeks before the current government got in," she recalls, "and a very, very exciting time to join the collection. I happened to be at No 10 on the Friday when the Blairs came in. I had to remove a painting of the cricketer W G Grace, left over from John Major's days." The defeated Tory prime minister had favoured paintings of a frankly idealised Britain, where girls played tennis in leafy, undisturbed rural settings. But Johnson describes how "we've made big changes at No 10. The portraits are now of contemporaries rather than 18th-century notables. Darcey Bussell is there, along with scientists and other achievers."
The GAC has its share of historical material. Down in the storage area, we walk past Oscar Nemon's wearily familiar bust of Churchill ("still much in demand"), a bemedalled bronze of the portly Edward VII and a white marble head of a quizzical-looking Wilberforce. But Johnson, with an annual purchase grant of £200,000, has ensured that far less predictable works are now entering the collection. Hanging in her office is a brazenly festive, boldly striped painting by Jonathan Parsons. "I love the frenetic element of it," she says, "and I bought another one for the consul general in New York because of the artist's reference to Mondrian's painting Broadway Boogie Woogie. I do like abstracts, and I find that they're very popular."
But Johnson and her advisory committee, now chaired by the broadcaster Julia Somerville, have also been buying a lot of photographic work. In the viewing area, she shows me A Machine for Living, Dan Holdsworth's photograph of a sinister, bunker-like building. "We felt photography should be much more represented, because it's accepted now. But I wouldn't advise anyone to hang prints in direct light. We don't buy vulnerable watercolours for that very reason."
Conservation is inevitably a major feature of the GAC's work. Walking through the receipt and despatch area, Johnson pauses by an enormous full-length portrait of Queen Victoria by Sir George Hayter. It looks robust enough, but she tells me that "it got buckled at the Washington residence".
Works of art in embassies and gov- ernment buildings are protected less clinically than in art galleries. Tropical climates can be especially problematic. Johnson shows me the metallic tape laid on the back of a painting "to prevent insects getting through - they can feast on a picture and, before you've noticed it, eat the entire frame away".
The recent upsurge in terrorist attacks poses another, far less predictable threat to the collection. Six works by the Crimean war artist William Simpson were destroyed in the recent Istanbul bomb blast that killed the consul general.
The past is not forgotten: Johnson lingers with pleasure over the recently acquired Portrait of the Broke and Bowes Families, painted in a naive yet sprightly style by Thomas Bardwell in the mid-18th century. "It's our first ever conversation piece," she announces with satisfaction, "and we hope that all our pictures will turn out to be conversation pieces wherever they hang." At the other extreme, the GAC now boasts a Damien Hirst print of gemstones, which was displayed for a while at No 10. Contemporary art can be intensely controversial, and Johnson must refer any potential purchase over £10,000 to her committee: "They have sometimes said no." But she is fully aware of pitfalls. "We don't want portraits of slave-owners, and we can't have swear words or blasphemy."
The finest paintings in the collection tend to occupy prominent locations. Paul Nash's surreal yet quintessentially English Event on the Downs, painted in 1934, is now displayed in Downing Street. And Johnson is particularly gratified when outstanding pictures match their locations in cultural or geographic terms. Joseph Wright of Derby's eruptive Firework Display at the Castel Sant'Angelo of around 1770 hangs in the British embassy in Rome, while Bridget Riley's Reflection, a multicoloured stripe painting inspired by her visit to Egypt, is installed in our Cairo embassy.
The more exquisite the setting, the more difficult it is to find appropriate images. "Sir Michael Jay wanted contemporary work when he was ambassador in Paris," says Johnson, "but it wasn't easy in such a historic house. After looking round, I suggested focusing on the ground-floor Glazed Galleries. So we took down the royal portraits and hung Callum Innes's Exposed Painting, Cadmium Red Deep, as well as a colour transparency and lightbox piece by Catherine Yass."
In her intensely luminous image of the embassy garden, Yass has included one of Johnson's most inspired acquisitions: a tall, columnar sculpture in lead and gold leaf by Shirazeh Houshiary. It looks ideally suited to its verdant Parisian location, and Johnson has found an equally felicitous setting for a large sculpture by Tony Cragg in the new Berlin embassy. She warms to the challenge of working with major new buildings. "At the moment, Tony Fretton is designing our new em-bassy in Warsaw, while Terry Farrell is doing a landmark Home Office building in London. He's working with Liam Gillick on a commission, and there'll be more new art outside and inside the building."
The GAC has clearly become far more adventurous since the timid old days when stuffy effigies of grandees were the norm. Johnson retains a discerning eye for history, and recently bought a portrait of the first British envoy to go to China. But she had no hesitation in spending a substantial amount of her annual grant on a new sculpture by Richard Deacon.
"A minister may still come in and say: 'We really like Ivon Hitchens - do you have one?' But there's far more interest now in contemporary work. Prints of hunting scenes are no longer in great demand."