The Duke of Edinburgh had to apologise to the then Tory prime minister, Mr Edward Heath, after making allegedly "anti-Common Market" comments at the height of the negotiations to take Britain into Europe, British cabinet papers revealed yesterday.
Prince Philip wrote to Mr Heath apologising "profusely" for causing "further trouble on this vexed question" after his comments on the impact of the Common Market on agriculture were seized on by the press.
In a note released to the Public Record Office under the 30-year rule, the duke said he was "appalled" at the furore caused by his remarks made at a conference in Edinburgh in June, 1971.
"At the time my mind was running on a completely different tack and I never dreamed that my comments could be construed as being either pro- or anti-Common Market," he said.
"I am afraid the mere words 'Common Market' have the same effect on the press as the bells had on Pavlov's dogs." Prince Philip had told members of the Royal Agricultural Society of the Commonwealth: "There are cases already within the Common Market where ancient and long-standing agricultural patterns have been completely up-ended as a result of the operation of the Common Market system in Europe."
His comments, understood as a stark warning for agriculture if Britain went into Europe, were deemed an inappropriate foray into one of the most controversial political issues of the time.
They were considered all the more astonishing because British delegates were attending key Common Market talks in Luxembourg at the time.
Buckingham Palace issued a clarifying statement, also contained in the newly-released file, claiming he had "always been careful" not to express an opinion on the subject.
The context of his remarks was "the danger of treating agriculture as if it was simply a manufacturing industry", it continued.
"His Royal Highness was not intending to imply that he expects these dangers to follow as a necessary consequence for Britain joining the European Commission."
In his reply, Mr Heath admitted the ensuing headlines gave him "a bad moment or two", but said that it "all proved to be a storm in a teacup and the record is now straight again".
He added: "I am sure you are right, as things are, the press will fasten on to any passing reference to the Common Market by any public figure, and there will be those who will be all too ready to read their own vices into even the most balanced and non-committal observation.
"I suppose it is all part of the 'great debate'" Mr Heath went on to advise the duke not to fly on Concorde until the results of forthcoming Mach 2 trials were known.
A flight by either of them could give the impression the government is "firmly committed" to the project going into production, he said.
Queen Elizabeth secretly offered to give up the Royal Yacht Britannia to help the government's spending cuts.
However, files released to the Public Record Office show that the offer was turned down by Mr Harold Wilson's Labour government.
The defence secretary, Mr Denis Healey - whose budget covered Britannia - warned Mr Wilson that it was essential that the details of the queen's offer were kept secret at a time of deeply unpopular public spending cuts. The offer came in a letter to Mr Wilson from the queen's private secretary, Sir Michael Adeane, dated January 2nd, 1968.