All this may give the Queen a rude shock when she opens the museum later this month. Britain's naval history has been adapted, rewritten and questioned. For more than 60 years this museum has chronicled how Britain's supremacy at sea was a vital force in shaping a nation's character and backbone. No longer. The iconoclastic approaches to empire and imperialism that saw Britain's rule of the seas as being based on little more than mercantilism (or piracy, if you prefer) is now centre-stage. The establishment - and you cannot get much more establishment than two of the museum's trustees, the Dukes of Edinburgh and York - are suddenly prepared to question everything about our military and mercantile maritime past, including our greatest maritime icon, Lord Nelson himself. Certainly, the Nelson gallery documents his life, death and victories at sea. But what is one to make of the flashing sign at the exit of the gallery, asking, "No more heroes? Who made Nelson? Is all this propaganda?"
Rear-admirals must be having apoplectic fits. One historian has already reacted. Lawrence James, author of The Rise and Fall of the British Empire, says: "It is an appalling representation of our past. Its sole purpose seems to be to champion the values of political correctness." He adds that children will leave the museum with no pride in their country and its achievements, but with a sense of shame.
Certainly, the museum goes out of its way to view some of Britain's imperial and class-conscious past as a matter of light comedy. As well as the screen showing a Carry On excerpt, there is, in a gallery devoted to transatlantic crossings, a life-size model of a first-class traveller and a voice-over sneering at steerage passengers; the key Trade and Empire gallery on the slave trade is dominated by a tableau of a lady sipping tea as a manacled black arm emerges from a grating. The visitor gets the explanation: "The slave trade was driven by the need for an English cup of tea." The Royal Navy's role in hunting down slave- traders after Britain abolished slavery - depicted in Steven Spielberg's film Amistad - is not mentioned.
James reserves his worst venom for the museum's director, Richard Ormond. "The original celebration of our seafarers' achievements clearly embarrassed the curator," says James. "He considered it too `old-fashioned' for the Blair age and unlikely to interest the young. For him, today's youth are simple-minded creatures with an arcade-game attention span. They could only be lured to the museum by exhibits that take their themes from multiculturalism and environmental awareness."
In fact, Ormond, far from being a Cool Britannia, politically correct video arcade enthusiast, is a scholar curator of the old school of museum directors. Tall, shambling, slightly detached and other-worldly, he has a whimsical way of talking with a half-smile, gripping you with a passionate enthusiasm and then going off in lateral directions, reminiscent of one of those eccentric but inspirational public schoolmasters. He sits in his office overlooking Greenwich Park, surrounded by books on maritime history. He agrees that what he and his staff have done to the museum is a seminal change. But he rejects all charges of political correctness. He does, though, agree that young people now - not least in the highly multi-ethnic catchment area of the museum - will simply not swallow the traditional teaching of Britain's imperial past. And so, yes, he is presenting it in a different way.
And so, with remarkable irony at a time when Britain is, through Nato, waging war, the country's one institution that celebrated maritime militarism is about to lead the way not just for museums to reinterpret their collections for a new generation, but for them to reinterpret both history and how we view heroism and the national character.
"I don't think we're ashamed of our past at all," says Ormond. "It is a mistaken notion that a museum like ours can demonstrate the whole of history in a holistic way. There's no way we can do the whole sweep of British maritime achievement. There's a new thesis and a new vision. Going through all these battles, you feel, after a while, that it's very repetitive in a way. Simply to celebrate naval victories and imperialist expansion wouldn't intrigue and interest our visiting public. We want to engage with the maritime world today, so we had to shift from a specific national identity to a wider sweep. You have to deal with environmental issues, pollution, rising sea levels. Those are the things that excite us and our public. Do you know, for instance, that 70 per cent of the world's population live within 50 miles of the sea?
"When we opened in 1937, war was looming and the sea was central to every aspect of national life. But that whole world of British supremacy at sea has vanished. The sea itself is just as vital today, but for different reasons. It's the playing off of the tension between that historical past and today's resources.
"The whole of the Nelson gallery is a paean of praise to a remarkable man. The words at the end of the gallery are really asking, do we value heroism today? But the museum needs to challenge traditional thinking. In the Armada exhibition that we mounted, if we achieved nothing else we did get across that it was the weather rather than British might that did for the Spanish fleet."
Underneath this revision of thinking, reflects Ormond, "was our sense that the sea was slipping away. We couldn't be seen as a specialist museum for people interested in ships. Strangely enough, there's more ignorance about how seafaring trade works today than about how it worked in the past. We want families to come, and nothing turns families off more than if children are bored. Now they can have a go at steering a Viking ship."
If the museum has moved some way down the road of political correctness, then the Duke of Edinburgh has been one of those approving it, though museum sources admit that the decision to have a Greenpeace pod in the wonderful new Neptune Court came only after a long and difficult debate among the trustees. Decisions to have displays on fishing, weather and climate and pollution, on plants and flowers (showing how they were brought here by voyages of discovery), on naval uniform fashion, and on a motor car (showing how its manufactured components come by sea) were not contentious. This, the Duke and his fellow trustees accept, is the way of getting the importance of the sea over to a new generation.
Ormond's deputy director, Roger Knight, spells out the Maritime Museum's new philosophy most plainly. He says: "Traditionalists may be uncomfortable. Where are the reassuring, massed displays, consistent reminders of Britain's supremacy, when the biggest and best ships carried Britain's naval power, trade and irresistible traditions to that part of the world upon which the sun never set? The answer must be that if they were ever there, those values were never a reality for a large part of the population and will never be accepted by the citizens of the next century."