SEARCHES in Gibraltar have previously proved unsuccessful.
In May 2002 remains were found at the Botanical Gardens, close to the dockyard.
But police quickly confirmed they were not those of 18-year-old Simon Parkes. More searches were carried out by police in 2003.
That included looking in a network of underground water chambers and caverns. Land off Trafalgar Cemetery was previously cleared and searched. Ground-penetrating radar was also used in the searches.
In 2006 a detective said ‘extensive research’ had been carried into the disappearance but added ‘we have drawn a complete blank’.
Today DI Roger Wood appealed to the public to help. He said: 'I am particularly interested in hearing from anybody who served on board HMS Illustrious back in 1986 and knew Simon Parkes, or knew of Simon at least, and can recall seeing him on the 12th December 1986.’
He added: ‘If we haven't spoken to you before we want to hear from you as you many have a little piece of the puzzle that we're missing that can help us answer the questions that we have and bring some closure to Mr and Mrs Parkes, Simon's parents, the wider family, and the navy.’
Call 101 quoting Operation Thornhill or visit mipp.police.uk and select the investigation.