The rebranding plan was prepared on the back of deepening resentment of Ireland and Irish brands in Britain, public relations chief Edward Guinness told embassy officials in London.

“Mr Guinness remarked that an association with Ireland was part of the Guinness image,” Paul D Dempsey of the embassy wrote.

“He was no longer sure this association with Ireland was helpful.

“They were encountering a lot of resistance to the Irish angle and this could force them to emphasise facts such as that Guinness was an English company which had its base at Park Royal. Indeed, they had publicity material of this kind ready during the Falklands crisis but had not used it.”

In the meeting on Aug 18, 1982, Mr Guinness, a descendant of the banking line of the family, refused to accept the views of diplomats that British attitudes to Ireland went through cycles and opinions would improve.

“In his view, the impact of these things was cumulative,” said Mr Dempsey. “The Mountbatten killing had a serious effect. The Falklands crisis and the IRA bombings had added to the damage.

“A fund of goodwill towards Ireland existed, built up in the 50s and 60s. This fund was being depleted.”

Mr Guinness, public relations executive for Park Royal brewery in London, told embassy staff that the Hyde Park bombing caused “particular offence” because it was an attack on the Queen’s guard and horses were seen lying dead.

The IRA’s July 1982 bombs killed 11 soldiers, four from the Blues and Royals and seven bandsmen. Seven horses also died.

“Furthermore, many people had been affronted by the fact the IRA were able, within a matter of hours, to put out a gloating press release from Dublin,” he said.

Mr Guinness urged diplomats to press the Government to speak out against the IRA.

“He cautioned against a policy of silence — thinking that because the IRA were not active it was not necessary to say anything about them,” embassy staff said.

“The Falklands crisis and the IRA bombings were associated in people’s mindsand it was desirable to keep reminding people that the Irish people were totallyopposed to violence and those who used it.”

Mr Guinness also relayed how the chairman of Tyne Tees television, a publican and brewer in Sutherland who bottled and distributed Guinness through his pubs, objected to being supplied from Dublin.

“If the dispute with him went public, it would not do Guinness any good,” he said.