"I understand that the prime minister has expressed concern about the implications of the Falklands Islands crisis for Gibraltar," one of her secretaries recorded in papers released to the National Archives as a result of the 30-year rule, "particularly in the light of reports of the jubilant reaction in the Spanish press." (The 30-year rule requires records to be transferred from government departments to the Public Record Office after 30 years unless specifically exempted.)
The Guardian, the BBC and other media outlets reported on the just-released documents about the 1982 crisis Friday.
A British military review of Gibraltar's position offered "a rather more reassuring picture," the private secretary said, adding, "We have no reason to believe that there is an increased military threat to Gibraltar from the Spanish government."
She expressed concern about a planned military exercise by Spanish forces, but the exercises went off without incident.
The 1982 invasion of the Falkland Islands by Argentina also caught Thatcher by surprise, the documents indicated.
The then-prime minister only saw it was likely after getting "raw intelligence" two days before the Argentinean forces landed.
In October 1982, soon after the conflict ended, Thatcher testified during a closed-door hearing.
"I never, never expected the Argentines to invade the Falklands head-on," she said in the just-released transcript. "It was such a stupid thing to do, as events happened, such a stupid thing even to contemplate doing."
Thatcher said intelligence indicating an invasion was likely was "the worst, I think, moment of my life."
As early as 1977 British intelligence indicated Argentine military action was possible if talks over the islands faltered. At the end of 1977, the British government sent a submarine and two frigates to the South Atlantic, although the vessels' movements were kept secret, the papers indicated.