Melanistic Black-headed Gull - Tynemouth

I was passing Tynemouth boating lake just before dusk and pulled over to work through the gulls. There were plenty of ducks including a couple of Pochard and Wigeon, and the usual contingent of Tuffties. The gulls all checked out as expected with mostly Black-headed  Gulls and a couple of Common Gulls.

But then, on a second scan "What the.................is that!"- I came across a Melanistic Black-headed Gull. It had me going for a very long second. Still, I've not seen one before - a 'mutant' tick.

Does it trump Johnny Kinson's leucistic Blackbird? I'll let you decide.