Tim Smit

As well as the Eden Project, Wikipedia lists two other Cornish tourist attractions that Tim Smit is "famous for his work on": the Lost Gardens of Heligan and the Charlestown Shipwreck & Treasure Centre.

Neither of these is as famous as the Eden Project, I couldn't swear to either of them being "brown sign destinations", and I also don't know what job title (if any) he has in relation to either of them. But either of them (especially Heligan) should probably have been allowed as alternative answers to this question.