John Major was warned it would be seen as a "snub" if he failed to attend a 70th birthday dinner for Margaret Thatcher.
Officials initially urged the Prime Minister to give the event a miss, expressing concern about Lady Thatcher's political "games", according to papers released today by the National Archives.
However, aides reluctantly changed their minds amid concerns it would go down badly with the Conservative Party if he skipped the bash.
Despite being her chosen successor when she quit in 1990, Mr Major had an increasingly difficult relationship with Lady Thatcher after he entered No10.
Nevertheless, he agreed to host a dinner in Downing Street in September 1995 to mark her 70th birthday.
He and his wife Norma were in turn invited to an event she was hosting at Claridge's three weeks later.
The PM's personal assistant Arabella Warburton pleaded for the invitation to be rebuffed, pointing out it would be the Monday after the Tory Party conference.
"Lord knows what games she'll be playing there. GRRR!!!" she wrote in a handwritten note.
Mr Major's principal private secretary, Alex Allan, was initially sympathetic.
In a note to the PM he said the premier will have "done Lady T proud" by hosting the Downing Street party, while the cast list for her dinner was "not that attractive" – even though it included the Queen.
However, he went on, after consulting others in Downing Street, the consensus was Mr Major should go.
"It would be well received by the party at large; if you declined when you had no other engagement it would look like a snub, notwithstanding your own dinner," he wrote.
In a handwritten note to Ms Warburton, Mr Allan added wearily: "Both PM & Norma will go (groan!)."
