shared driveway

Access

My property shares a driveway with next door that leads to both garages. I recently spoke to the tenant and he was told that it was only their driveway (which is legally false as in the deeds it is shared access) and his landlord has put a padlock on the gate at the start of the driveway (which for the record is never locked).
Ive recently put up a wooden gate and fence for privacy as both lounges,kitchen etc faces eachother. I will agree that when the gate is closed it does look like the driveway belongs to nextdoor...

Am i wrong in thinking that the landlord is trying to 'steal' the whole driveway? Can he succeed in this?
Am i wrong in putting up a fence and gate as it could be used against us if the landlord next door says it is only his? Worst case scenari;o i will remove fencing etc or put them on hinges/retractable...
Should i take photos over time/dated showing my car up the drive and me using my garage etc etc

much appreciated for any help