We are one of the oldest democracies. And yet we have a system of land registry and a pattern of land ownership that put us back in the age of Gilbert and Sullivan. Even then, when the Duke of Plaza-Toro was prancing across the D’Oyly Carte stage, people did at least know who owned the land in Britain.

There have been only two occasions in the past one thousand years when land has been fully registered. Once when the Domesday Book was compiled 20 years after William the Conqueror invaded in 1066. The second, 800 years later, in 1872. The so-called Return of the Owners of Land managed to register every acre in England and Wales. Today’s Land Registry is able to tell you who owns only 50% of the land. The other half is unregistered. (Scotland is different, there land registry is much more comprehensive.)

In just over 130 years more than 30m acres have mysteriously gone missing. Take the Duke of Wellington: back in 1872, the 2nd Duke is registered as owning 15,800 acres. Today the Land Registry has no record of his holding. So in our research for the BBC programme Whose Britain Is It Anyway?, we wrote to the current duke and asked him how much land he owned. He declined to tell us. The Land Registry is hoping to persuade him and those who own the unregistered half of Britain to own up by 2012 — its target date for full registration.

This curious lapse in our registration system means that we can only estimate who owns the land today. There are 60m acres in England, Wales and Scotland, roughly one to each member of the population but I was startled to find, first, that 90% of us live on less than 10% of the land and even the plots we inhabit are shrinking. Second, just under one-third of Britain’s land is still owned by aristocrats and traditional landed gentry. Ordinary British homeowners (freeholders) who have greatly increased in number over the past two decades are competing for land that gets tighter and dearer by the day.

We in Britain live in smaller spaces than anywhere else in the 15 countries of the old Europe. Housing statistics show that in 2002 Britain’s newly built dwellings had, on average, the smallest floor areas. Part of the reason we cannot afford to buy bigger houses and bigger gardens is that the land is simply too scarce. It’s there but it’s not made available. There are vigorous planning restrictions that forbid the release of all but a tiny trickle of greenfield sites for housing development.

We cannot, by the way, blame the big landowners for this. Many aristocrats would be delighted to sell off a few acres of land for development: it’s the planners who stand in the way. There are those who argue we are too protective of our countryside and that, far from being starved of rural acres, Britain is actually less urbanised than Germany, Holland, Denmark and Belgium. They want to ease planning restrictions and give people more space. It is a radical and challenging argument, with the political consensus at the moment heavily stacked against it.

Land reform is not a burning issue for most of us. There is no sign of any new peasants’ revolt marching up Whitehall. Indeed the irony is that political parties of both colours have moved full circle on the big land issue. For much of the last century governments exacted a level of death duties so penal that huge estates had to be sold off. Now the tax regime is far more lenient. There is a whole raft of tax breaks available to landowners who recognise an obligation to conserve the land and make it and their properties accessible to the public.

Only in Scotland has there been any measure of real land reform. Crofters are now allowed to buy their freeholds at a reasonable price. The Duke of Buccleuch, Scotland’s biggest landowner with nearly 300,000 acres, calls this “shameless, legalised theft”.

For the rest there is a shift going on in the ownership in land edging us away from the classic divide between crown, church and aristocracy. Each traditionally owned around a third of all British land. We estimate that over the centuries church land has dropped down to just 1%. Much of the glebe (local church land) has been sold off to defray parish expenses.

The crown is now reckoned to own just 1% of Britain too. Only the aristocracy has maintained its slice of national land. In the 19th century one of Britain’s great landowners, the Earl of Derby, famously described land as bringing “political and economic power, social status and pleasure to its owners”. Today the aristocracy no longer enjoys political power but it still owns 30% of the land and still enjoys some of the perks Derby referred to.

In London that is slowly changing. It’s a long way from the day when the ambitious Tom Grosvenor married Mary Davies for her dowry of five fields and a bog just west of Buckingham House. That became Belgravia, the heart of the great Westminster estates, and three other great aristocratic families (the Howard de Waldens, the Portmans and the Cadogans) acquired huge swathes of London’s West End. But the Leasehold Reform Act 1993 is now nibbling away at these great empires. Tenants with longer leases are now able to buy the freeholds. The Duke of Westminster was so outraged by this attack on his land that he resigned the Tory whip in the House of Lords in protest. The ice is moving.

The main gainers in ownership of land have been the Forestry Commission and heritage organisations such as the National Trust. The most striking feature of the flow of funds across the land is the way in which taxpayers and members of the public who pay to visit stately homes and parks are helping to finance its conservation.

One of the things I greatly enjoy is looking up the guides to houses, castles and gardens that list the places that receive money from the government but are open to the public by appointment only. I like to put this to the test by phoning up and asking for a time when I can visit. The heartening news is that they are usually most accommodating.

The fact is that although very few of us can claim to have direct ownership of much of Britain, for all its quirks and curiosities the system of funding gives each of us a claim to have a stake in rather more of the land than we think.

Whose Britain Is It Anyway? is on BBC2 on Tuesday at 9pm