An Edelweiss Airbus A340 entoute from Zurich to Punta Cana was cruising over the UK when the crew squawked 7700. The aircraft entered a holding pattern most likely to dump fuel and is currently at 8000 feet and it appears they will make an emergency landing in London UK. The nature of the emergency is unknown at the moment...
Update: The flight appears to have landed safely at London's Heathrow Airport.
https://www.flightaware.com/live/flight/EDW34N