Who owns the “green and pleasant land” of the English countryside can be a well-kept secret, in part because a large segment of it does not even figure in public records. Government efforts to make a public accounting of land ownership date to the 19th century, but according to the Land Registry, about 15 percent of the country’s area, most of it rural, is still unrecorded.

“Much of the land owned by the Crown, the aristocracy, and the Church has not been registered, because it has never been sold, which is one of the main triggers for compulsory registration,” the registry, which covers England and Wales, says on its website.

Mr. Shrubsole began documenting England’s estates after the referendum on Britain’s withdrawal from the European Union, known as Brexit, in 2016. “If Brexit really meant ‘taking back control of our country,’ then I’d like at least to know who owns it,” he wrote in an op-ed in The Guardian a year after the vote.

Real estate prices in England are among the highest in Europe and have soared over the last generation. Mr. Shrubsole’s book documents ownership, maps unregistered land and argues that the concentration of ownership helps keep available land scarce and expensive.

Houses, stores, office buildings, schools and farms are often held under long-term leases, paying a steady stream of rents — directly or through intermediate leaseholders — to major landowners.

Mr. Shrubsole said that by publishing his research, he wanted to start a conversation.

“It should prompt a proper debate about the need for land reform in England,” Mr. Shrubsole said. The issue of land relates to the country’s housing crisis, to economic inequality, to climate change and the intensive use of farmland, he added.

The ancient idea that wealth meant land does not always hold true in modern times. But in Britain, land accounted for half of the country’s net worth in 2016, according to data from the Office of National Statistics — double that of Germany and higher than in countries like France, Canada and Japan.