Found this on
http://www.timlaw.supanet.com/
BTCC Time Line
1958
The first series of the British Saloon Car Championship was run by the British Racing and Sports Car Club and was divided into four classes:
1. up to 1200cc
2. 1201 to 1600cc
3. 1601 to 2700cc
4. 2701cc & over
1966
New regulations introduced relaxing restrictions on tuning and modifications to suspension, although stricter rules governing bodywork were instigated.