Reproduced in 'Drawings by Kennaway: a medley in line and wash' (The author, 1959), page 35 with this caption:

Sweetnes and Light

Sweetness: "My old man has given me a couple of quid and I don't know whether to get a perm or get my teeth fixed up."

Light: "Oh get yer perm, yer can always keep yer mug shut."

Overheard on a Christchurch bus.