'Upgrading' to skinny tyres pointless for London commuting

You'd need to be optimised in so many other ways first before that up-to-5W saving at 50km/h comes into play.

That's like saying you might as well ride old school until you've done under 50 minutes for 25, because you're never going to get comp record on any bike until you can do 30mph on 1970s tech.

As gains go, swapping from butyl to latex has to be about the cheapest in W/£