Keep the French “in the dark” and raise “three cheers!” to our American allies emerge as recurrent themes in top secret documents debating how to secure advanced military technology during the 1980s.

Files released to the National Archives in Kew on Friday show how UK ministers favoured the US shuttle launch system for military satellites over Ariane rockets.

A 1983 memo from the Ministry of Defence to the prime minister warns there is “French pressure on us to be ‘European’ and go for Ariane”.

Margaret Thatcher agreed that it was better to go with the American shuttle, which was cheaper and had a better safety record.

The MoD wanted to send two Skynet 4 military satellites, manufactured by BAE and Marconi, into orbit to provide communications across Europe and the Atlantic.

The shuttle launch was priced at £58m – £23m cheaper than Ariane.

“We [currently] rely on American cover for the command and control of all our naval forces outside the UK, including submarines and surface task groups and our forces in Falklands, Lebanon and Berlin,” the letter, highlighting the UK’s reliance on US goodwill, informed the prime minister.

The French Socialist prime minister, Pierre Mauroy, wrote to Thatcher pleading for the decision to be reconsidered and offered to reduce the cost. The issue, prefiguring the Westland helicopter affair, escalated into a diplomatic row over the UK’s international priorities.

Geoffrey Howe, the foreign secretary, wrote to Thatcher in December 1983 advising caution. “If we opt for the shuttle,” he said, “we must expect the French to make a fuss.

“Indeed, in the wake of the [European Community] Athens summit, they may be looking for an issue to illustrate an alleged lack of European commitment by the UK and may therefore choose to make even more of an adverse Skynet decision than would otherwise have been the case.

“There is therefore a case for keeping the French in the dark for a time about a decision to go for shuttle in an attempt to distance it from post-Athens discord.”

Eventually the French were told the US bid had been chosen. When the next military satellite launch in 1986, however, Ariane was favoured. After the Challenger shuttle disaster, a No 10 memo stated there “is no other option but to use Ariane”.

Another top secret prime ministerial file on Project Moonflower is worded in such an obscure manner that its so-called black subject is not immediately apparent.

President Reagan and Margaret Thatcher in 1981. Photograph: AP

President Ronald Reagan was offering Downing Street a briefing on “highly sensitive … technology with a view to the United States and the United Kingdom working together on it”.

“Dear Margaret,” a 1986 US telegram recorded, “I am delighted to hear that you will be able to see Cap [Casapar Weinberger, the US defence decretary] to discuss the special program I wrote you about … I look forward to receiving your reaction. Sincerely, Ron.”

In a top secret personal message, on which someone wrote in faint pencil “STEALTH”, an enthused prime minister wrote back after the secret meeting: “Dear Ron, I was immensely impressed by your splendid achievement: three cheers for America!

“I was also very touched by the generosity of the offer of participation which [Cap] brought. It brings home once again who our real friends are … I am so much looking forward to seeing you in Tokyo. With warmest best wishes, yours sincerely, Margaret.”

The offer of transatlantic cooperation on Stealth technology – which disguises an aircraft’s presence from radar detection – was one the MoD declined to take up.

An MoD letter in December 1986 to Charles Powell, the prime minister’s foreign affairs adviser, about Project Moonflower informed him that “Mr Weinberger has offered us a chance to purchase the current US aircraft but we have replied that we would not wish to actually buy hardware while the programme remains strictly black [secret].

“… [George] Younger [defence secretary] raised the subject very briefly with Mr Weinberger this morning … just sufficiently to test whether Weinberger is disappointed at our reaction so far. He certainly does not seem to be.”