If you're in a situation where you quite reasonably know that a call to the Police was necessary, and the kids mum (your gf) isn't agreeing, you're asking for relationship and personal grief if you allow your own standards of what's right n wrong to be comprised. I'm an old bugger who's been step dad more than once. Frankly; in the long run, getting your FAL is a minor worry compared to the grief ahead if you allow said crim to set the rules. You're no mug. You're asking advice and that's bloody good. Stay with what is good and true. And communication is important. Relationship, life and general advice session over. PM me if this resonates.
Bookmarks