Porsche took its evaluation of a potential works Formula 1 project so seriously that it had 40 people working on the early stages of an engine programme, but in the end its interest cooled. Scott Mitchell and Edd Straw discuss how serious Porsche's interest in F1 was, why nothing happened in the end, and what it means for F1 to have missed out on landing a high-profile fifth manufacturer for its 2021 revolution