Shared water supply - how can I prevent my neighbour turning my water off

[BlueShadow]

Hi, My neighbour and me share water supply. My neighbour let's the property out. We were discussing work he did to fix leaks on the pipe-I am insisting on a report/plan as per my insurers request. The neighbour hasnt been co-operate and was threatening litigation. My T junstis under neighbours house I have been told. However the main issue is that on the day I was insisting again on a full report my water went off mysteriously. Long story short is someone switched off the water in the house so he must have a stop cock in the house. Not sure if this is a new installment in the leak fix or was there originally. Is neighbour allowed to have this control over my water supply-he left me without water till the next day, how can I get him to remove the stopcock or reposition it so it only affects his house. Surely it cannot be legal that he can switch my water off at a whim. Thank you

[BlueShadow]

*junction. Oh the property next door is empty.