If you need a single answer for a form, a school admission, or a database: Greater London. Stick that in the box. If you’re writing a love letter to history: Middlesex. If you’re trying to settle a bet with a grumpy cab driver: both, but expect a five-minute rant about “the good old days before the ’70s.”
Personally, I think Enfield is in a county called Confusion—but that’s just me. The next time someone asks you, just smile, pat them on the back, and say: “It’s complicated, mate. Grab a pint and I’ll explain.” Then watch them nod off after the first sentence about the Local Government Act of 1963. Job done.
And remember: if you ever feel lost about UK counties, just blame the Victorians. They started it.