Bought house 3 years ago, terraced house.
One side of garden fence is the one with the issue. This possibly shared fence (deeds just state boundaries, not who's responsible for it). Has an access gate (Vendor had paid for this gate and some fence panels, receipt was in with the various paperwork when we bought the house. Unsure if gate was a replacement or new).
Access has only been used across the neighbours back garden once or twice a month maximum by our Gardener and to put the garden waste bin out. It's not ever used whilst they're in the garden and no damage has ever been made to their garden. (They don't maintain their garden; overgrown with grass, brambles and nettles. Rubbish also dumped in there).
They've now put a lock on the gate fence so that we can't use it. We asked why and they said they didn't want us to use it. We've asked them to remove it nicely which they've refused. (They're not nice neighbours).
We really need the access in the summer (rarely used if at all Oct-Mar). We don't want to have the gardener taking the lawnmower through our house each visit or want to do the same ourselves with the garden bin).
To add neighbours moved in just over a year ago. Previous tenants had no issue with us using our gate.