Margaret Thatcher's aides found themselves dealing with an "odd complaint" ahead of a meeting with the French president in 1979 - that his chair should be of "equal status" to that of the prime minister.
The bizarre exchange of telegrams and letters was made public today after thousands of confidential papers, which were kept under lock and key for 30 years because of their sensitive nature, were released by the National Archives in Kew, west London.
President Valery Giscard d'Estaing came to London for the bilateral visit on November 19 1979, and one of his engagements was a meeting in the Cabinet Room at Number 10 Downing Street.
The wooden chairs used by Baroness Thatcher and her ministers were part of a set, but officials of the French head of state noticed during a planning visit that the prime minister's seat had arms, while the rest of the chairs did not.
Clearly keen to ensure their political leader was treated no differently to his UK counterpart, the French "quite seriously" insisted on a chair with arms.
The issue was first raised in a letter dated November 7 1979, from Andy Wood in the Downing Street press office to the prime minister's personal secretary for overseas affairs, Michael Alexander.
He wrote: "In all seriousness (first three words underlined) the Elysee party pointed out that they would consider it essential for the President to have a chair equal in status - i.e. with arms - to the Prime Minister.
"Alternatively would the Prime Minister swap her chair for a 'regular' (i.e. armless) model?
"Sorry about this - the French made the point quite seriously."
However petty the issue might appear, even senior ministers became involved.
In a confidential telegram entitled President Giscard's Visit, sent in November 1979, foreign secretary Lord Carrington urged the British ambassador in Paris Reginald Hibbert to have an "informal word" with the general secretary of the French presidency Jaques Wahl to resolve the matter.
He wrote: "The advance team from the Elysee who were over here earlier this week came up with an odd complaint when they looked over the arrangements at No 10.
"They claimed that the President would not accept arrangements which meant that he was sitting on a chair which was not of equal status with that of the Prime Minister."
Lord Carrington went on to write that no other head of state has ever complained, and it was unlikely Giscard would have raised the issue, considering he used an armless chair in the Cabinet Room on a previous visit.
"In any case we have never come across this problem before despite the many Heads of State and Heads of Government who have been to No 10, and we find it difficult to believe that the French complaint does in fact reflect the wishes of the President himself," he wrote.
"We are not aware of any complaint on his part after his visit to London in 1976 when the Cabinet Room was used.
"We and No 10 should be grateful if you would have an informal word with Wahl when you see him tomorrow to try to get this little matter sorted."
In response, a telegram was sent to the Foreign Office from Mr Hibbert on the November 9 1979 entitled President Giscard's Chair.
"I took this up with Jacques Wahl this afternoon and to my surprise encountered considerable resistance," he wrote.
"In the end he said he would look into the matter further. The decisive consideration might be whether other French Presidents or President Giscard himself had previously accepted the seating arrangement without comment.
"I was able to draw his attention to the 1976 precedent of President Giscard himself."
The ambassador then quotes Mr Wahl's reaction of "Dieu soit loue", translating as "Praise be to God", which suggests the French aide's considerable relief when he realises the President has sat on an armless chair before in the Cabinet Room.
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