Dan Wieden says
http://wklondon.typepad.com/welcome_to_optimism/2005/02/words_from_wied.html

And Russell Davies reprises…
http://russelldavies.typepad.com/planning/2006/07/7_things_i_lear_1.html

And then continued…
http://russelldavies.typepad.com/planning/2013/04/the-unit-of-delivery.html

Thanks Russell.