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Tauranac designed the Theodore Racing F1 car for the 1978 season. Two new designs were created for the 1979 season: the RT2 for Formula Two and the RT3 for Formula Three. The RT3 chassis won the 1983 European F3 championship for Pierluigi Martini and five consecutive British F3 titles. A joint venture with Honda resulted in the RH6 chassis, which won the 1981, 1984 and 1985 titles. In October 1988, Tauranac sold the Ralt business to March Engineering for £1.25 million.