Chris used his F1 experience to develop the Tasmin for competition use, achieving pole position in its first three outings at Oulton Park, Donington and Cadwell and seeing great success in the 1986/87 season winning 21 out of 24 races.

At the end of the 1987 season, the SEAC was banned on grounds of homologation (not building the 200 cars required).

The acronym SEAC stands for Special Equipment Aramid Composite, which means that more than 20% of the body was kevlar unlike the other wedges, which used full fibreglass construction.

Other differences between the SEACs and the 350i/390SE/400SE wedge line include: a different chassis with a narrower transmission tunnel (1 or 2 were built with stainless steel chassis); the handbrake being changed to an umbrella type handle under the dash; a flat, 4 gauge dashboard; the exhaust system having twin pipes routed under the rear differential rather than a single pipe routed above it.

The use of kevlar and the highly tuned Rover V8 engine made the car extremely quick but had its effect on price, which was twice as much as a standard 350i.