The Late Arrival

You are a consultant at a large advisory firm. On a regular Monday, you notice a senior partner, who is usually punctual, arrive late to a client meeting; an hour later, another consultant asks what might have happened. Work out how you would investigate the cause, gathering information discreetly and without making the partner uncomfortable.

A good answer should identify the proximate cause of the unusual lateness by testing plausible explanations discreetly, then explain the evidence and quantify the added stop time.