TWR developed a kit for privateer teams to make the XJS competetive in endurance racing, but Jaguar were so impressed they took the kit onto the factory race teams, and it became a long standing partnership. Jaguar actually gave TWR 12 cars for them to upgrade and sell as promotional tools. They are very rare, I have not seen one for years, if it is a gen car it will go for a fortune!

Early pic of the TWR cars