Hi Andy
The Birkett Relay Race is a lot of fun

Andy (ESL) has competed twice, when it used to be run up at Snetterton, although it is held at Silverstone these days. I think we managed a class win on one of those years?
The racing members of Harrow Car Club put together a team from the club membership (and sometimes one or two guests from outside the club). It is a handicap race so there is really no limit to what can be out on the track - all cars must be closed wheels (open wheel / closed wheel cars are not allowed to mix in races) and have the mandatory safety stuff (roll cage and hand held fire ex minimum).
Because of the wide range of speeds of the cars (I think there could be as much as a 100mph speed
difference at the end of Revett at Snetterton between the Austin 7s and the muscle cars!!!), you need a minimum number of races under your belt before you can compete - I think the minimum requirement is either a National 'A' race licence or 8 races experience on a National 'B' race licence. There are ways of getting these though - each year Harrow is eligible for the Eight Clubs races (which unfortunately were cancelled this year!!!) which can get you two races experience, then more experience can be gained through something like the RAF MSA grids. I think the Peterborough MC run general closed wheel race events that anyone can enter also.
I was going to post up about the race meetings this year but the cancellation of the Eight Clubs poured cold water on the idea. Hopefully it will be back next year with a vengence!
I had proposed a Big Power Birkett relay team elsewhere on this forum but got no response!