Removing an easement is not straightforward - especially since the whereabouts of the legal owner of the land is impossible for the LR to find.
The best bet is to claim the land through adverse possession but I'm afraid you are going to have to bide your time to effect a final outcome. Once you've claimed the land in this manner, the presence of the easement becomes rather irrelevant!
The following link to Practice Guide No. 4 from LR may help.
http://www.landregistry.gov.uk/assets/library/ documents/lrpg004.pdf
This will download one of a series of PGs published by LR - for registered land. If you find it tough going, here's a precis.
The law changed for registrered land in 2002 in respect of claiming adverse possession - what the popular press insist on calling squatters' rights. Now you can make the initial claim after 10 years - not 12 - at which point the LR make efforts to find the registered owner. If they can't or if the registered owner does not oppose the claim, the land can become yours after a further 2 years.
The leaflet gives you clues to what you have to show to claim Adverse Possession. Basically you fence it and maintain it - nothing fancy - get an industrial strimmer in then cut the 'grass' as paddock, perhaps. Take some photos at regualar intervals of you enjoying your 'new' land. Lewis cutting the grass - Cherie in a deckchair, perhaps. All these things help.
Come back in 2017 and tell us how you got on.