A Land Title number is the Land Registry’s unique number for a property. Every property registered with them has one, which makes it a convenient way to consistently refer to the same site.
How to find the Land Title number for a property
From the Ownership layer, click on the parcel of land
Click the green “freeholder” button
The number will appear (and serve as a clickable link to directly purchase the document
Note: If you’re on the Starter or Pro plan, this will use one of your ownership views
Unlimited users have the added bonus that they can export ownership information for all sites (useful for things like mail-merges).