Secret files have revealed that UK defence chiefs considered turning the North Sea into a minefield in the 1970s amid fears that terrorists would hijack a rig.
Senior military figures expressed “considerable concern” that extremists could attack an offshore platform or try to hold its workers to ransom.
Secret records, which can be made public for the first time today, show they believed Palestinian groups had “actively considered” targeting a western oil and gas installation.
Security officials warned at the time that the Soviet Union had an “undoubted” capability to carry out an attack on the country’s North Sea interests and that it could not be ruled out.
Mining the waters and stationing armed troops on the platforms were discussed in draft strategies as ways to prevent any terrorist strike.
The plans were being drawn up around the time the first North Sea oil was coming ashore in the mid-1970s and are detailed in files at the National Archives in London, seen by the Press and Journal.
Many of the records are marked “SECRET. UK EYES ONLY”.
An April 1974 document, under the heading “Action To Counter A Terrorist Threat To An Offshore Installation in Peacetime”, said: “In the present climate of terrorist activity there is a danger of an extremist threat to an offshore oil and gas installation.
“This could take the form of a direct attack or, more probably, a hijacking.
“Any such operation would require a sophisticated level of support and planning, but it is considered that a group of armed trained saboteurs would, with suitable helicopter or surface transport, be capable of occupying a rig and holding it and the crew to ransom.”
A unit of commandos from the Royal Marines was suggested to undertake any operation to regain an offshore rig.
However, the drafts make it clear that an overt assault would be “extremely hazardous”, requiring support from armed helicopters and ships, while a clandestine operation at night with dinghies and underwater swimmers would also “present considerable difficulties”.
The use of mines was recommended in a document discussing possible ways to defend the North Sea platforms.
Palestinian groups were named as the most capable of carrying out a terrorist attack, potentially in reaction to a shift in UK foreign policy involving Israel. The Black September organisation had recently kidnapped and killed 11 Israeli athletes at the 1972 Munich Olympic Games.
As part of the “second draft” of the strategy, a note written in September 1972 includes an assessment of the risk posed by the Britain’s Cold War adversary the Soviet Union.
“Discussing the relevance of North Sea oil, it was noted that if the Soviets regard oil rigs in the same category as ships, they might attack them,” it said.