I was under the impression P1 was already permissive, I suspect Northern / platform staff wouldn't stop in the correct position to allow another service to arrive though.The same arrangement used when a 12 car 350 calls, platform 12. There is an aspiration to clear platform 1 for permissive working to allow them to use that with the Northern services. The benefit being that it doesn’t have to cross the entire WCML on departure, which doesn’t do performance any good.