DH recently left his employer for another. A junior colleague asked him where he was off to and if they had any other jobs going. DH advised colleague should approach new employer direct. The colleague subsequently had an interview and accepted a job. DH was asked for his opinion of the colleague by new employer. But otherwise had no involvement. Ex boss now knows they're both headed to the same place and is threatening to sue DH and new employer. Does he have any grounds? I've read about anti-poaching clauses in contracts but don't think DH's contact had this. DH genuinely tried to keep out of things as thought this could happen, as let's say the ex employer has form for things. DH just wants a clean start away from them!