The London pub—historic haunt of revolutionaries, writers, and politicians—is under threat. Its numbers have fallen by a quarter since 2001, with the steepest drops in central London. Yesterday, London’s mayor launched an audit of the city’s public houses to figure out ways to stem the losses.

It’s no coincidence that pubs have closed in London’s central districts, where property prices have soared. London house prices have risen threefold on average since 2001. Pubs often occupy prime locations on the high street and are a target for corporations who want to convert them into more lucrative shops, residences, or office space.

Take the example of the nearly 300-year-old pub highlighted by the mayor’s office. The China Hall in east London’s Rotherhithe district was acquired by developers a few years ago. Now its operators, a couple who have run the pub for 37 years, are being presented with a new lease that’s double what they currently pay. They either have to find the money or leave.

What’s more, developers are allowed to convert a pub into retail or office space without seeking permission from the local council, making them attractive to large retailers. For example, the Campaign for Real Ale, a pub pressure group, estimated (pdf) that the supermarket chain Tesco converted 37 pubs into shops between 2010 and 2014. The group wants lawmakers to change those planning rules.

London’s pubs contribute jobs and tourist dollars. More than half of international visitors to the city visit a pub, and they provide a first job to a sixth of people aged 18 to 24, the mayor’s office says. Pubs in London employed 46,300 people in 2016, according to government figures.

It’s not simply a case of pubs getting priced out of London. Myriad other factors, including how pubs are taxed and a decline in beer consumption, make it increasingly difficult for London pubs to stay in business. London’s new Night Czar, Amy Lamé, tasked with figuring out a solution, launched a public consultation on the issue April 19. She could do with some help from those habitués of London’s pubs, Engel and Marx, who came up with their own solution to the head-scratchingly difficult problems of their day over a pint at the Red Lion in Soho 170 years ago.