Talk:McLAREN P1™/@comment-137.186.237.13-20170302060055/@comment-4939977-20180602175841

Did you complete Road to Le Mans? Once you completed RTLM, Vertex will unlock, which will then show you the number of trophies you needed to win to unlock HHC (Endurance Kings is an instant unlock upon completing Road to Le Mans). Win the trophies needed and HHC will unlock for you.

I had the same issue with the Group C bonus series but I didn't complain at all. I just needed enough trophies in McLaren Generations for those series to show up.