Walnut tree 60cm from building - can it stay or not?

[dent123]

I have a 15 year-old self-seeded walnut tree, with a height of about 10m, which is on the boundary between me and my neighbour. It is about 60cm from a single-skinned outbuilding on my land, about 3m from my 2-storey extension, and about 5m from my neighbour's house. There is a 1.5m drop near the tree so ground level is uneven around its base. Photo attached. There are substantial roots near the surface, one of which has already put a crack through the foundations of a nearby patio.

 

I want to get rid of the tree, primarily because I plan on replacing the outbuilding with something new, but I'm inclined to think that even without doing that the tree has reached a stage where it poses a risk to all the nearby buildings. My neighbour wants to keep the tree and proposes that reducing it in height and thinning it out will be sufficient to remove any risk. Some people have told me I'm mad to even think about keeping it, and others say it will be fine with a bit of attention now and then to keep it in check, so I don't know what to think now! I think I should get it professionally assessed - what should I look for in an assessment which would satisfy anyone involved (e.g., building control, future purchasers, insurers, neighbours, etc.) that either the tree poses no risk to property, or that it must be condemned?

 

thanks.