Hi Duncan - you can apply to register the easement on the servient land/title using form AP1 along with supporting evidence as appropriate
Easements (PG62) - GOV.UK
I would however recommend seeking legal advice first to confirm the legal position for you, and others, re the right to consider what's need to put the owner of the servient land on notice and/or to register the right on their title
Land registration is complex, designed to protect legal and financial interests in property. There can be significant consequences for any error. Please consider seeking legal representation. Before making an application without legal representation, it is important to
consider the benefits of using a conveyancer.