When I had my car log booked I did not have a cage installed in it. From memory it is logged as a 3 RCO (Rally Car Other).

The CAMS office here sent me out a package that included a document that explained what was required to get B Reg. Again from memory it was as simple as organising for a scrutineer to come look at the car and sign a form which you then take to CAMS along with a 3/4 front and 3/4 rear shot of the car. They then issue a log book. Once you have that you take the log book plus your proof of ownership and your car to the pits and they can issue the registration.

Everything I hear from people trying to do it these days suggests that it's not as easy as it used to be for some reason. My car was done in early 2008.

Edit: Just saw Fred's link to Brendan's post. Sounds like you're screwed now unfortunately.

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Ben
Evo IX GT