Thanks for that clarification Cartman.
I declared a medical emergency to Shanwick 2 weeks ago during a transatlantic sector. They were very helpful and relayed our problem to London and allowed us to increase to our max mach.
On handover to London, the controller advised that there was currently a 15 minute arrival delay into LGW and if even though he understood that we had a medical emergency, unless we declared a pan or mayday, then we would not be treated as a priority.
We declared a pan and were treated expeditiously by London as a priority.