574. Estoppel and abuse of process.

Where the issue of validity has been determined in the claimant's favour and a subsequent claim is brought against the same defendant, the defendant may be estopped, as a defence to the proceedings, from challenging validity even on new materials1. If the issue of validity has been determined in favour of the patentee but the patent is subsequently revoked at the instance of a third party, the defendant is estopped from challenging any order as to damages which has already been made2. Similarly, if the issue of validity has been decided against the claimant, he cannot bring a fresh