Sunday Times
The Sunday Times' style magazine crowned U.S. first lady Michelle Obama the best-dressed woman in the world earlier this month, and the newspaper's ad agency, Grey London, created this ad to promote the title.
It's a simple idea, nicely executed:
If Obama was the monarch, what would Queen Michelle look like in profile on a 1st class Royal Mail stamp?
(Britain has lots of different stamps of course, but it always sells a "basic" version with Queen Elizabeth II in profile.)