Can't remember the date exactly, but the Harrier was on a test flight out of Dunsfold.
A/c climbed to 2000ft on a westerly hdg, conatcted Farnborough for climb. Duly arranged by Farnborough controller with LTMA CSC and the (then) HURN CSC.
A/c then climbed to FL330 (?) rapidly, still HDG west. Nothing more heard from pilot, a/c continued westerly track. D&D alerted.
An hour or so later a USAF C5 Galaxy was vectored alongside the Harrier and reported that "there was no-one in the cockpit". They videoed the Harrier continuing west, with seat, a broken canopy and no pilot. It eventually ran out of fuel an crashed in the Atlantic.
Several days later unfortunate pilot's body was found on Salisbury Plain somewhere
As I recall the seat had fired the drogue through the canopy for some reason with fatal results. There was some speculation about a loose article ( red light?) and the pilot adjusting the seat height.
Others will know more, but that's as I recall it.
Bestv rgds
BEX