Students don't need any excuses
What merits an acceptable pretext for staying away from the office? Work-experience students can skive at the slightest excuse - a trip to an important new building, for example, or a nice lie in the park - on the basis that nobody can ever think of anything for them to do.
Year-out students can cite an interview for Part 2, bringing the logbook up to date, the death of a pet - employers tend to be grateful if they can kid themselves that the year out is actually an informal arrangement and that the salary is generous, as opposed to exploitative.
Qualified architects need a better excuse. Funerals are acceptable, but cannot be used too often. Doctors and dentists will suffice only if you are in visible pain. Alternative medicine should always be sampled in your own time.
'Waiting for tradesmen' is legitimate if a drug-crazed lunatic has kicked down your door, but not if you are interviewing a cleaner, or receiving advice on feng shui.
Directors are entitled to spend as much time as they want in the pub. The privilege is justified on several counts:
they are so involved with the company it is meaningless to distinguish between work and play; their creative intellect needs to be fed by the freeflow of ideas; there is nobody more important to grass them up to; and the rest of the office gets much more done, and has a much better time, when the boss is out of the way.