giafly writes "Damages for patent infringement awarded by a UK court must not be paid back even if the patent is later declared invalid by the European Patent Office (EPO), the Court of Appeal has ruled
... "Now a purist may say: it is a nonsense, and moreover an unjust nonsense, for a man to have to pay for doing what, with hindsight, we know to have been lawful," said Lord Justice Jacob. "But I think there are good and pragmatic reasons why the purist approach makes bad business sense. You cannot unravel everything without creating uncertainty." — Out-Law"