'And that means they have to ask permission. The essential decencies must be maintained,' said Ridcully firmly. 'And I am the Master of this college!'
'On the subject of, er, decencies, sir, you are not in fact wearing-'
Ridcully strode through the open doors of the Library. 'What is going on here?' he demanded. The watchmen turned, and stared. A large blob of foam, which up until that point had been performing sterling service in the cause of the essential decencies, slipped slowly to the floor. 'Well?' he snapped. 'Haven't you lot seen a wizard before?'
A watchman snapped to attention and saluted. 'Captain Carrot, sir. We've, er, never seen so much of a wizard, sir.'
Ridcully gave him the slow blank stare used by those with acute uptakegrasping deficiency. 'What's he talkin' about, Stibbons?' he said out of the corner of his mouth.
'You're, er, insufficiently dressed, sir.'
'What? I've got my hat on, haven't I?'
'Yes, sir-'
'Hat = wizard, wizard = hat. Everything else is frippery.'