My DP's colleague threatened to "punch his lights out" at work today. DP immediately reported the incident to their manager, who has promised a meeting first thing on Monday to sort everything out. Problem is that the incident wasn't witnessed by anyone else, so it's his word against his colleague's. DP does not want to work alongside this colleague any more, and he does not think he should put up with this sort of behaviour from the colleague.
Should DP insist on HR being present at the meeting? What else should he do to prepare for this?