Grimson, dubbed the Frankenstein killer for his hulking 6ft 2in frame, was jailed for life in 2001 for killing Nicholas Wright, 18, from Leicester, and Sion Jenkins, 20, from Newbury, Berkshire.
Naval rating Simon Parkes was just 18 when he vanished without a trace in the final leg of a worldwide deployment on Navy ship HMS Illustrious in 1986.
Royal Navy Rating Simon Parkes, from Bristol, was last seen drinking at a pub in Gibraltar after the ship the 18-year-old was serving on, HMS Illustrious, docked
Simon Parkes, from Bristol, was last seen drinking at the Horseshoe Pub on Main Street after the ship he was serving on, HMS Illustrious, docked in Gibraltar in December 1986.
Simon Parkes, from Bristol, was last seen drinking at the Horseshoe Pub on Main Street after the ship he was serving on, HMS Illustrious, docked in Gibraltar.