Simon's isn't just an ordinary Chesil, either;
Massive Type 4 engine to make it really go,
Four wheel power disk brakes (944's I think) to make it really stop and he's using a remote hydrovac (power booster) over on the passenger side.
Here's a shot from Simon's photo files on here of the power booster (you may have to cut and paste to get it to work, or go to shambly under the photo section and look at the last photo at the bottom:
https://www.speedsterowners.com/files/view.asp?sf=shambly&f=brake%5Fservo%2Ejpg