The sign hanging on door of room 101 of the Hotel Miramar on Tuesday morning was carefully worded to avoid arousing any suspicion about the events unfolding inside. It read: "Do not disturb, my children are ill."
It was only when the reception at the £53-a-night, four-star hotel in the Costa Brava resort of Lloret de Mar was called shortly before 2pm by the room's occupant, 43-year-old Lianne Smith, with a request to call the police and an ambulance that the horrifying nature of what had taken place became clear.
According to Spanish police sources, investigators entered the triple room to find the bodies of 11-month-old Daniel Smith and his sister Rebecca (5) lying on a bed covered by blankets.
Their mother, who had arrived at the hotel by car a day earlier, had written a note in which she allegedly confessed to killing her children.
Yesterday, it emerged that the road to this tragedy had begun 10 days earlier when detectives from Spain's Guardia Civil had arrived at the family's rented apartment in central Barcelona, some 50 miles south of Lloret de Mar, and detained Mrs Smith's husband, Martin, for extradition to Britain on paedophilia charges.
Media reports said that the housewife had told police -- who are investigating whether a plastic bag was used to asphyxiate the two infants after they had been subdued using over-the-counter pain killers -- that she feared her children were about to be taken away by the Spanish authorities.
Martin Smith (45) a television psychic, had been placed on a list of Britain's most-wanted fugitives in September last year after he left the country during an investigation into sexual offences against a girl aged under 16 between 1995 and 2005.
He is thought to have fled the UK in December 2007 with his wife and Rebecca.
Officers moved to arrest the businessman on May 7 after information was received by Operation Captura, a joint initiative by Britain's Serious and Organised Crime Agency, Crimestoppers, and the Spanish authorities aimed at capturing wanted Britons thought to have fled to Spain.
Police are investigating whether Mrs Smith, apparently distraught at the arrest of her husband, carried out the killings to coincide with his deportation back to Britain on Tuesday.
Smith yesterday appeared in court on 13 charges including rape and sexual assault, hours after being told of the deaths of the two children.
Police sources said Smith was "distraught". There were conflicting reports as to whether Smith, who is the father of Daniel, was also the father of Rebecca. Mrs Smith has four children, at least two of whom are from a previous relationship. It is understood the claims against Smith do not relate to Rebecca.
A police spokesman said: "During the court hearing it was disclosed that Smith's wife, 43-year-old Lianne Smith, has been arrested on suspicion of the murder of the two children."
The couple are understood to have settled in the Carlisle area in 1999 after Mrs Smith's previous relationship had ended. The businessman, who was born in North Shields, worked for a management consultancy and had previously had a job as a sound engineer before he set himself up as a professional medium around 2004.
The psychic seemed bound for a high-profile career when he was approached in 2007 to appear on The Most Haunted series, for the satellite channel UK Living, on which he claimed to have sensed a baby at a spot where the programme later revealed that a woman had killed herself and her child by jumping from a bridge.
The family are thought to have left Cumbria in 2007 and settled in Staffordshire, while police were investigating the allegations of sexual assault against Smith. When he failed to answer his police bail in January 2008, it was found he had left the country month earlier with his wife and Rebecca.
Although police rapidly formed the opinion that Smith had fled to Spain, the trail went cold until this month when detectives were pointed in the direction of an apartment building in Barcelona which the couple had rented. Operation Captura, which publicises wanted Britons using posters and a website in Spanish, featured Martin Smith in a list of 10 fugitives released last September.