In the 80's, Swindon had the lemon curd!
The lemon curd was a Ford Granada Scorpio 2.9l with some serious engine mods.
It was used (rather famously) in the chase that started in Bath, headed east along the M4 and terminated in the Heathrow tunnel. The chase lasted just 40mins IIRC and ended when the car being chased blew a tyre. The car being pursued? A Ford Sierra Cosworth!
I had a browse around the net lunchtime and couldn't even find a picture!
I think it was a Scorpio, not a Granada, and the roof lights were concealed under some body coloured fairing IIRC