fictitious character

[egordon]

which fictitious advertising agency createdby a famous writer of detective stories in one of her best novels came up with a slogan for margarine which read 'its a far,far butter thing'

[ChocClare]

Pym's Advertising Agency in Murder Must Advertise by Dorothy L. Sayers.  I think.  Haven't gone through the whole book to check.  But it sounds like one of hers!

[Westminster]

Pym's Publicity was the name, as I recall; but like ChocClaire I haven't checked.

[woofgang]

I have, it is, what a fabulous book. The copywriter in question was Mr Death Bredon, aka Lord Peter Whimsy