Thomas Dennis was joint venture between Thomas Built Buses, a subsidiary of Freightliner, of the United States and Dennis, part of Mayflower Corporation, of the United Kingdom. The company was formed in 1999.
In 2003, Thomas and Orion Bus Industries were purchased by DaimlerChrysler and became part of DaimlerChrysler Commercial Buses North America. The SLF 200 was sold under the SLF 200 brand through Orion's sales network. Mayflower had hoped to develop a 40 foot transit bus, however with the sale of Orion to DaimlerChrysler, Mayflower sold its 49% stake in the company.