Dinah Casson set up her design practice in 1970 and her partnership with Roger Mann in 1984. Since 1992, Casson Mann has focused most of its work on the design of museums and exhibitions. These have ranged from the object-based British Galleries at the V&A and the Great North Museum in Newcastle, through to the highly technological Churchill Museum in the Cabinet War Rooms and the Lord Ashcroft gallery at the Imperial War Museum. During the last 6 years, they have designed projects in the UK, US, Russia, Italy and the Middle East. Their work has been published extensively and has won numerous awards.  

Dinah Casson is a trustee of the Creative Education Trust, The Charleston Trust and, with Roger Mann, was elected to the Faculty of Royal Designers for Industry in 2006 of which she is currently the Master.  In 2013, Dinah was Master Elect of the Faculty of Royal Designers for Industry. Since the 1970s, she has taught at design schools such as Kingston University and the Royal College of Art.