Is my Tarmac trespassing?

If this was me then my first port of call would be to see what your freehold title deeds say and what his say, to see if there's anything in either about the exact boundaries.

As they're old buildings this may not bring up any joy, in which case he could argue that the 300mmm of tarmac is his land. If so then what's that got to do with you? Why would you have liability for his issue on his land - you never even placed the tarmac there in the first place. Who knows what was agreed at the time it did go down.

Sounds to me like he's looking for someone to pick up his cost. If the problem doesn't go away, I'd take legal advice.

Reply to the comment left by Neil P at 07/02/2024 - 10:17Thank you for your post. I think it is his land but as the tarmac has been down over 20 years, I could claim it by adverse possession. But the cost would be prohibitive and then maybe it would make me liable for the cost of the work.
I have legal cover with my insurance but they are asking for a surveyors report. If I pay for that and then they say they don't cover this type of claim anyway, I may as well put the money towards the remedial work.
The title deeds aren't helpful

The good news is that the work itself is straightforward - use a cutter along the tarmac, excavate out with a spade and backfill with shingle. If you do that though, I'd be wary you're not inadvertently accepting responsibility...and he'll be after you to fix the inside timbers etc.

Just because his eaves overhang doesn't mean that the land under that overhang is part of his ownership. This is quite a common situation and as a former Building Surveyor, I have come up against these arguments often. The title Deeds are a starting point, but do not rely on Land Registry title plans as these are only ever considered to be indicative. What's on the ground, who has had the accepted responsibility of maintaining this land and what the original paper Deeds say about ownership, access to neighboring land for repair and maintenance etc.
Is the wall that the nieghbour is complaining is damp the original 'as built' wall or a subsequent extension to the house? If the latter, then they should have made reasonably provision in the construction in anticipation of this situation if the land on your side of the wall was at a higher level. If however, and notwithstanding if the whole drive is yours or not, It is unlikely that your drive would have been constructed to a level higher than your nieghbours DPC/floor level if the wall was there at that time, so would suggest that the drive has either been built up or the neighbour has extended close to or up to the boundary without consideration of the effects.
You say that yours is a HMO, is there also an element of resentment in your nieghbours claims, maybe? Establish the boundary first, establish if the neighbours wall is a result of an extension or alteration to his premises and take it from there!

It is not unusual for insurance companies to deny liability in legal protection cases. My experience was once you have taken some initial legal advice, from your own pocket, that indicates that there is a genuine issue that also falls within the scope of the policy they will change their on approach liability.
Disillusioned Landlord gives you some sound advice, boundaries are not always definitively defined and overhanging eaves less so.

Reply to the comment left by Disillusioned landlord at 07/02/2024 - 10:47The neighbours wall is the original wall of the side of their house (circa 1900) and is not an extension. Its a long house going back further than average. They have already repaired their timbers and I don't believe there is an issue of resentment that they live next door to flats. The deeds are not helpful as there is no plan and as you say may not be reliable anyway. Its interesting that the eaves argument is not relevant.
The tarmac along the side of my block allows pedestrian access to the rear flat through 2 gates which are fixed to their property. They want them removed and the width of the access reduced by the width of the excavated trench. This would leave quite a narrow pathway for access which has been used since the flats were converted in the 90's

Why not lower the whole path and retarmac? Believe me this will be a great deal cheaper than any litigation.

Reply to the comment left by at 07/02/2024 - 11:18It seems ATM, the insurance company want me to pay for a surveyor's report 'to confirm the boundary location' and they 'will not cover costs of obtaining proof of boundary if that is the dispute'.
The neighbour is now saying that if the remedial work is not something I am prepared to do as 'a gesture of we would like to explore the possibility of splitting the cost'. Failing this they say they 'have little choice but to instruct solicitors at significant cost to both parties'.
An initial estimate for the works is £2,000 so that seems rather silly.

Reply to the comment left by TheMaluka at 07/02/2024 - 11:36
Excavating along the boundary, and supporting the earth would be cheapest - its not on a slope - possibly only a matter of inches too high.
It would be silly to have a legal battle over this. If I were the neighbour, I'd pay for the works. I have an almost identical issue with another property a couple of hundred yards up the road but the other way round. It didn't occur to me to ask my neighbour to pay!

Reply to the comment left by JB at 07/02/2024 - 11:40
Avoid Litigation.

Litigation will cost a great deal more than doing the work, especially if your neighbours agree to split the cost, and it is likely that you will have to do the work anyway.