The freehold estate
Law Commission/HM Land Registry (2001) Land Registration for the Twenty-First Century: A Conveyancing Revolution, Law Com No. 271, available online at http://www.lawcom.gov.uk/project/land-registration-for-the-21st-century/, paras 2.7, 11.5–11.19
This Law Commission/HM Land Registry report introduced the LRA 2002. You can see here details of provisions about Crown land.
https://www.gov.uk/government/organisations/land-registry
This is the website of the Land Registry. It features publications explaining land registration and you can look at the forms required to register land.