C S Lewis was fond of concealing things at times, apparently, for instance the planetary basis of the Narnia series - each book represents symbolically one of the seven medieval planets, i.e. the ones visible to the naked eye.
In the introductory section of the book Planet Narnia, where Michael Ward is demonstrating that concealment, while not necessarily a defining characteristic of C S Lewis' character, was something he sometimes practiced, the discoverer of this surprising allegorical underpinning of the Narnia series Michael Ward points out an instance of C S Lewis telling a lie.
Apparently there was a fox hunt and C S Lewis deliberately misled them:
'He cupped his hands and shouted to the first riders, "Hallo, yoicks, gone that way," and pointed to the direction opposite to the one the fox had taken. The whole hunt followed his directions.'
A rather endearing lie, if you ask me.