The crew declared an emergency at 1:pm BST (squawk 7700).

The flight is operated by a Boeing 777-300ER (registration N2737U).

UPDATE 13:12 BST
On approach to runway 27L.

UPDATE 13:21 BST
Flight #UA926 has safely landed on runway 27L at London Heathrow.

UPDATE 13:23 BST
Going to terminal 2 gate B46.

UPDATE 14:56 BST
Flight #UA926 is resuming the flight to Frankfurt following the medical emergency.

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