“It is relatively well known that if T-marks are within your land that you are usually responsible for the repair of those boundaries”.
https://www.fieldfisher.com/en/insights/clarifying-the-significance-of-t-marks-on-a-plan
But that doesn’t stop informal arrangements between neighbours to do...
It's a myth that the fence to the left is your responsibility, there is no such general rule.
Around here, it's to the right.
Check out the plan with the title deeds to check for the little T's - where on your side, that fence is your responsibility.
Good idea from an earlier poster about...