The Secret Services warned the PM of the potential attack ahead of a summit in Paris in 1982, where she was due to meet the French President Francois Mitterrand. The summit was to discuss the European budget, as well as improving defences against the Soviet Union and even to discuss plans for the Channel Tunnel. But now newly declassified papers show a slew of security threats and terror attacks by middle eastern terrorists groups and far-Left french radical groups, which security forces felt could have put the former Prime Minister in danger. The papers show a series of killings across the content, including an American military attaché who was assassinated in January of the same year, as well as a train bombing which killed five that March.

Six more people were killed in August at a mass shooting in a Jewish restaurant and a car bomb in September injured more than 50 people. But just days before the former Prime Minister was due to travel to France, the private secretary for Francis Pym, Roger Bone, wrote to Thatcher’s defence and foreign affairs private secretary, to reveal that the UK ambassador to France had “expressed concern” over the safety of the Prime Minister, the Telegraph reports.

He had done so expressly “in the light of recent terrorist incidents in the city”. MI5 was subsequently ordered to carry out an assessment on the possible dangers, and they concluded that the risk of travelling to Paris was “substantial”.

Mr Bone wrote in a now declassified letter: “You will see the assessment [by MI5] is that there is a ‘substantial risk’ to the Prime Minister and that ‘the advance publicity which her visit is likely to receive increases that risk.”

The assessment was passed to Thatcher’s personal close protection team, and even to the British Embassy in Paris itself. A protection officer, as reported in the Telegraph, even flew to the French capital to discuss the possible dangers with French security forces.

“Nevertheless,” Mr Bone wrote, “you may consider that the threat assessment should be brought to the Prime Minister’s personal attention.” He added: “We shall of course keep a very close watch on the situation between now and the time of the summit and shall let you know if there is any change in the assessment.”

However despite the concerns of MI5, Thatcher chose to attend the summit as planned, which passed without incident.

Just two years later the Iron Lady found herself targeted by the IRA, who bombed the Brighton Grand Hotel during the 1984 Conservative Party Conference.

Whilst she escaped unscathed, however five people died and 31 were seriously injured.

The Telegraph reports that the French president was due to be welcomed to the UK just days after the bombing, but French intelligence chiefs worried about the safety of doing so.

Declassified papers show that a French intelligence officer even plants bombs in central London in a bizarre test of British security measures. Ministers were told that a police-led search on the French ambassador’s residence led them to find “two small containers of high explosives”.

Thatcher was astonished at the subterfuge of the French. Minutes of government meetings say the devices “had been placed there by a French security officer who was in London in connection with the president’s visit, apparently to test the efficacy of British security measures”.

The French officer was questioned but no formal charges brought.

Official cabinet minutes recorded: “The failure of the French government to explain, let alone apologise, for what had occurred was astonishing, and made it difficult for the British government to comment without appearing critical of the French during President Mitterrand’s visit.”