She is the owner and managing director of Mathmos, the lighting company founded by Edward Craven Walker, inventor of the lava lamp.
Granger took over Mathmos in 1989 and won two Queens Awards for Export.
After buying out her business partner David Mulley in 1998 and created with Mathmos Design Studio new ambient lighting products both in house and in collaboration with external designers.
Granger was part of the Government Innovation Review Committee with James Dyson and Terrance Conran in 2003.
She has sat on selection and judging panels for various design bodies including 100% Light, D&AD Awards and Design Nation Awards.