On a chilly Friday afternoon, a shirt-sleeved Neil MacGregor is in his element, beaming and basking amid the coated throng in his Enlightenment Gallery. People are handling objects at one of the curator- manned tables, puzzling at the labels in the large cases, gazing at the statuary. They're like children playing with a new toy, trying all the knobs to see what they do and then having another go. "You see, it works!" MacGregor exclaims, clasping his hands in something like glee, as a man with a child pouched on his chest brushes past to get to a case of archaeological fragments. "They're discovering!"
Yet this permanent exhibition is just as it would have looked 200 years ago. The newest British Museum gallery, around which MacGregor is showing me so enthusiastically, is also the oldest, sited as it is in the glorious neoclassical room that once held the King's Library, George III's collection of 600,000 antiquarian books. The display is set in 1800, an age of discovery that MacGregor, the museum's director, has set out to recreate.
And not just here in Bloomsbury, in London. On Monday, in tandem with a spectacular new acquisition, he will announce the latest step of that mission, a programme to take objects on tour around the country. But his broader plans for the museum place it, not just at the centre of Britain, but at the centre of the world as the leading international museum. That aim was given the highest stamp of approval when Tony Blair, opening the Enlightenment Gallery in December, announced that the Government would give the museum pounds 1m for its Africa Project.
That was a glittering end to the museum's 250th anniversary year, and one that MacGregor couldn't have dreamt of at the start of 2003, a year that saw an extraordinary turnaround in fortunes.
"What we want to show in this room is the way in which the study of things in a museum shapes our understanding of the world," he says, showing me a long, detailed label. "These labels demanded a certain amount of input from the reader, and that's what we've done here - you bring elements of your own experience to what you see.
"The point was to put into one room what Europeans could know about the world in 1800 - the organisation, the comparison and the study of things that actually allowed the Europe of the time to completely rewrite the way the world functions."
In 1700, such a room would have explained the systems of the world only by the Bible and the texts of the classical world. Then empirical study based entirely on research taught by the Enlightenment in the mid-18th century slowly destroyed the authority of those texts. "It must have been terrifying for them," MacGregor says.
The British Museum, both a product of the Enlightenment and a conduit of it, was the first national museum in the world. Created by an Act of Parliament - "So it's the people's museum, not a royal possession," MacGregor says - it was based on material sold to the nation by the physician, scientist and collector Sir Hans Sloane, who died aged 93 in 1753, the year of the museum's foundation.
Sir Hans had been George II's physician and had attended Pepys on his death bed. He made a fortune importing cocoa from the West Indies to make chocolate, and used his money to indulge his passion for collecting. He was an indefatigable traveller throughout Europe, and knew Newton and Voltaire. He had offered his collection to France, Sweden and Germany; he didn't mind where it ended up, as long as everyone had free access to it.
The 18th century was a neoclassical age, but the sculptures are Roman copies of antique Greek works, because that is what visitors would have known as classical before Lord Elgin brought the real thing from the Parthenon in Athens in 1802.
We stand in front of the giant bowl that is the gallery's centrepiece, supposedly a piece of Roman marble, although most of it was done by Piranesi in the 1760s. …