Bob owns and lives on a piece of land adjoining another, vacant one owned by Alice. There is a sheep fence between them which Bob has installed at his own expense (even though he legally could demand Alice to contribute).
There is Rob who owns some cattle and Alice allows him to graze them on her land, despite that they know the fence won't necessarily keep the cattle in.
One day one Rob's bull breaks the fence and makes his way onto Bob's land, causing some other minor damage too.
Who is responsible for the fence and other damage caused by the bull? Alice? Rob? Both?
Would the answer change if Rob was a close relative to Alice e.g. her adult son?