Our cat is 6 months old and called Ferdy.  We have 2 other older
female cats, who are farm cats and live outside.

Ferdy does not get on with the other cats, although it has not been a
problem as he lived in the farmhouse.

He has started to visit the farm nextdoor, we have had him neutered
and tried keeping him in, but everytime we let him out, off he goes
again.  Can anyone suggest anything to encourage him to stay at home,
as he is crossing a busy road to get to the farm nextdoor.