Had a big tough old collie cross years ago, who would 100% back me up, if anyone was about when we were out lamping he would come very close to me and start up his low growl. Me and him spent a weekend in Tidworth police station once and the coppers had to fetch me out my cell everytime they wanted to go in the kennel, they were sh*t scared of him
He could be a nasty bugger but good at his job.