Usually real estate companies or the original developers. It creates all sort of opportunities for abuse. Most of these long term leaseholds have a symbolic rent (“peppercorn rent”) though unscrupulous developers started setting up contracts with an initially small rent but with a steep contractual step up over time (most people do not read the small print). The servicing of the property is also often a way to squeeze leaseholders. The landlord has control over the servicing company and can overcharge through the service charge.

There are some projects of laws to remediate this mess, but this requires to overwrite private contracts, something gvts have been reluctant to do so far.