Yesterday evening was perfect.
Once I'd gone through the Blackfriars hell, and hit the 'open road' at Kennington I got into a bit of a chase situation with another cyclist and a moped. The moped guy was egging us on, saying cyclists couldn't keep up. Both of us cyclists looked at each other and rose to the task accordingly, and we both kept him in check from Oval down to Tooting Broadway, where I turn off.
I got 5 x PBs on Strava segments, and an average speed of 17.7mph over 9 miles - stopping at all reds!
The other cyclist was cleated up and on a carbon roadie. When we got to Tooting he said 'mate how the fuck do you go that fast in trainers?'
So the question is - do cleats make a huge difference to speed? I don't do long rides, so it'd only be for a city commute...