This paper reports on the design of three novel products: a hand saw, electrical plug and bicycle wheel. Each case study draws on interviews with the designers and analysis of their prototypes. The focus is on how the product ideas originated, how and why they changed and why those changes weren’t made earlier. In emphasising the nature of creative work throughout long and complex projects, three themes are emphasised: (1) creative challenges and creative blocks can result from earlier breakthroughs (which makes them difficult to overcome); (2) multiple design spaces co-evolve at different levels of detail (not just simple problem- and solution-spaces); (3) those developing new ideas need to recognise and accept those ideas (not just generate and develop them)