Please plead temporary insanity

So, you're Robert Webb. Star of the award-winning BBC3 comedy series 'The Smoking Room' (not seen) and the frequently brilliant C4 comedy series 'Peep Show' (seen, and could watch again and again).

You've got cred, fame, respect, admiration...

So, why skip merrily after Alexander Armstrong down Advertising Avenue - appearing in one ad for the Nationwide and, worse still, providing a voiceover for another for McDonalds - unless you've got zero principles and you're doing it solely for cash?

Answers on a postcard (or in the comments box below).