'Upgrading' to skinny tyres pointless for London commuting

Why dont you take some time to get an argument correct, otherwise you just make a fool of yourself, 28c has much lower rolling resistance than 18c, especially on rougher roads. However as stated before they are not necessarily faster due to added drag and weight...

http://www.analyticcycling.com/ForcesTire_TireRollingResistance.html

Rolling resistance is hardly given the wind-tunnel test by normal people,....instead, it is felt. Yes, if rolling resistance is defined as friction, then your argument (and Ed's) is correct; but if you add increased rotational weight as a factor to resistance, and not just friction, then the common experience is one that others share with me.