The voyage was protected by a detachment of Royal Marines and marked the culmination of a top-secret, UN-backed mission to ensure the huge stockpile of mustard gas ingredients amassed by Col Gaddafi did not fall into the hands of Islamic State in Iraq and Levant (Isil).Fighters loyal to Isil, also known as Daesh, seized swathes of the north African country last year, raising fears that the weapons could be plundered and used by the militants. Isil fighters have regularly used the weapons in Iraq. Experts said the Libyan chemicals represented one of the largest stashes of its kind in a rogue state.Col Gaddafi’s chemical weapons were destroyed under international supervision in 2014, however a quantity of precursor chemicals that could be used in the manufacture of weapons remained in the country.Earlier this year, the Libyan Government of National Accord asked for help from the Organization for the Prohibition of Chemical Weapons (OPCW) to remove the chemicals and destroy them abroad. Hamish de Bretton-Gordon, a former British Army officer and chemical weapons expert, said: “There’s been a very sophisticated operation going on to remove these chemicals. It’s a very significant day.”A very large amount of chemical weapons are now in the relative safety of coalition ships, where there was a view some time ago that they could fall into the hands of Islamic State.”Libyan officials said the stocks had been stored in the central Jafa area, about 120 miles south of the Isil stronghold of Sirte.The country developed a formidable domestic chemical weapons programme under Col Gaddafi. When he declared his stockpiles as part of his rapprochement with the West in 2004, he admitted having 25 tons of sulfur mustard, 1,400 tons of ingredient chemicals and 3,500 unloaded aerial bombs. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. There’s been a very sophisticated operation going on to remove these chemicals. It’s a very significant dayHamish de Bretton-Gordon His conventional weapons were looted by rebel factions in the chaos that befell the country after Col Gaddafi was toppled in 2011 by UK-backed rebels, but sources said the chemical weapons stocks had remained intact.Michael Fallon, the Defence Secrtary, said: “RFA Mounts Bay will help ensure chemical weapons precursors do not fall into the hands of extremist groups, including Daesh.“This contribution underlines our support to the Libyan Government of National Accord.”Samples of the chemicals have also been sent for analysis at the top-secret defence laboratories at Porton Down. Islamic State fighters seized swathes of Libya around the coastal city of Sirte last year A Royal Navy ship has helped destroy the last of Col Muammar Gaddafi’s chemical weapon stockpile to ensure it does not fall into the hands of Isil terrorists.RFA Mounts Bay escorted a shipload of chemical weapon ingredients through the Mediterranean from Libya, for destruction in Germany.The 500 tons of chemicals on board a Danish transport vessel represented the last of the former dictator’s reserves.