indeed, and can only do so without "breaking" any locks or windows (so it isn't "breaking and entering," which is the legal name of burglary.)
A properly secured property, where you make sure all windows are repaired and doors and windows are locked, is basically safe from squatters, assuming you get all the entrances (many old Victorian houses have common loft spaces, so when residential squatting was legal people could find one unlocked door in the street and claim a whole terrace. I heard of a priest who did it once in Lancashire somewhere and then used the row as almshouses.)
A properly secured property, where you make sure all windows are repaired and doors and windows are locked, is basically safe from squatters
A common tactic is to do it in two passes. First one dude comes along, smashes in the locks and walks away. Then a couple of night later a second group of dudes come along and find the house unlocked and 'legally' move in. So you basically have to have security people check your buildings at least once a night.
A properly secured property, where you make sure all windows are repaired and doors and windows are locked, is basically safe from squatters, assuming you get all the entrances (many old Victorian houses have common loft spaces, so when residential squatting was legal people could find one unlocked door in the street and claim a whole terrace. I heard of a priest who did it once in Lancashire somewhere and then used the row as almshouses.)