Covenant to not obstruct accessway

[Pinkes]

I want to buy a property that has an access way to a garage at the rear. The land that is the access way is owned by the neighbour at the rear (North of the access way) who granted a covenant in 1965 to provide my prospective property with vehicular access and ensure it is not obstructed. The deed plan says at least 8'6" wide. My direct neighbour, a pub, was at the time the grantee of the covenant although they didn't take on any obligation to not obstruct it (they owned my property back then). The pub is on the South of the access way and has trees on their rear boundary which have grown very large and have over time changed the line of the boundary so that the trees and also their fence have squeezed the access way so that it is no longer 8'6" wide. It barely fits my vehicle, particularly in the corner section, I've tried it and it's very very tight indeed. I can get my vehicle down there, but only just and the situation is only going to get worse. The pub is not covenanted to not obstruct it. But their rear boundary no longer reflects the shape/line drawn on the plan. I'm not sure how to resolve it beyond asking the pub owner nicely to cut his trees down (I can imagine the answer) or asking the landowner who is bound by the covenant (large freeholder landowner of an estate of maisonettes and I don't even know how to contact him) to ask the pub owner to do the same. And as this has been the case for a number of years now, can they legitimately refuse to do so, under adverse possession or something like that? The trees are not protected by TPOs. I want if at all possible to avoid some sort of time consuming and costly legal bid to enforce a covenant, particularly as doing so will involve the property of a 3rd party. But what is the legal position? Is the covenant still valid? Is it even possible for the servient landowner to fulfil his obligations given a 3rd party is obstructing it? Are there implications for me in trying to enforce it? Is there an indemnity that could get during the buying process that might be able to support me and what support would an indemnity actually provide?

[atticus]

This is going to be the source of endless problems for you. If this access is important to you, my advice is to walk away.

[sandfordboy]

100% agree with Atticus.