The PIA 'divert' was actually pre planned into MAN before the no diverts notam, and even though it said 'diverted' on the arrivals board, it was actually 'scheduled' into MAN.
With it looking likely LHR having some issues in the next few hours, the no divs notam may be lifted, as a few longhaulers low on fuel may be looking to get in. (although that may constitute an 'emergency' so may let them in anyway)