The breach of the secrecy that had surrounded the exact destination of Mr Major, who flies out today, has meant an immediate tightening of security at the farm. The newspaper gave a detailed account of the location of the 200-year-old house which has belonged to the Symington family from Britain since 1890.
But the Cabinet Office is also said by sources in Whitehall to have insisted that a thorough search of the house should be carried out to ensure that it has not been bugged. A government electronic surveillance expert was carrying out the search at the end of last week.
The move follows more than a year of controversy over the exploitation by newspapers of clandestine recordings of private conversations of prominent people, including leading members of the Royal Family, and David Mellor, the former Secretary of State for Heritage. The Government is already planning to outlaw such recordings. Mr Major was also embarrassed by the reporting of a pirate video of a private conversation he had with ITN's Political Editor, Michael Brunson, four weeks ago.
The Sun's report boasted that the newspaper had already been given a 'guided tour' of the house in advance of the visit by Mr Major and his wife, Norma. They are expected to stay in the house for a fortnight.
Mr Major's decision to go to Portugal, where his former foreign affairs private secretary, Stephen Wall, is now the ambassador, is a switch of countries for the Prime Minister. He has previously stayed at the Spanish home of Tristan Garel Jones, the former Foreign Office minister of state.
The Sun told its readers that there were no double beds in the house, that a previous visitor had encountered a 'four-foot snake' in one of the lavatories, and that there was a 'vast' wine cellar. It predicted that the residential staff would serve the Majors 'typical Portuguese food' such as goat, cured ham, cod croquettes, black bean salad and trout.