If you've never ridden Clement No. 1 Seta Extra tubs at 130psi, you haven't lived!
I still remember the sound of these on the concrete slabs of the Southend Arterial Road in the early 1980s - like someone tearing silk cloth next to your earhole! 8)
I use small chainring with smallest sprocket and cut the chain so that there's no loose looping and the chain goes from the bottom of the lower jockey wheel to the bottom of the chainring without touching any other part of the rear mech.
Yup, I believe that RTTC still don't insist on one, although most competitors use an aero one on the straight roads. However, with hill climbs, they serve no aerodynamic purpose.
IIRC, Richmond Park is 10.8 miles as a road circuit and there are occasional time trials around it.
Swinley Forest / Look Out is also a fave trail of mine. 8)
I occasionally let someone try them for a minute or so (like an MTB mate who had never ridden SPDs before) but they never take them far away from my sight.