forensic psychologist Joe Sullivan

Two British experts on sex offenders arrived in Portugal yesterday to help in the hunt for the kidnapper of missing Madeleine McCann.

The forensic behavioural analysts from the Child Exploitation and Online Protection Centre, which combats paedophiles, were sent in response to a request from the Lisbon Government. The Foreign and Commonwealth Office said that their arrival would ensure a range of experts was available to explore "every possible avenue" that may have led to Madeleine's disappearance.

One of the two British experts is the forensic psychologist Joe Sullivan. Mr Sullivan has helped police in Britain and Europe to investigate child sex murder, abduction, organised paedophile rings and underage internet pornography.

He formerly dealt with paedophile priests at the Lucy Faithfull Foundation, a child protection charity that strives to assess and treat abusers. He has published a study into professionals who abuse children. Its conclusions included the striking finding that one in seven paedophiles, including priests, admits choosing vocations to enjoy easy access to children.

Last night John Buck, the British Ambassador to Portugal, confirmed that British experts had arrived in addition to the three family liaison officers from Leicestershire Police.

Mr Buck also defended the actions of the Portuguese police, saying that they had to operate under the constraints of the country’s law.

He added: "I have been in touch closely over the last few days with the cabinet minister here in Portugal and the Prime Minister and Portuguese police. They all assure me that everything possible is being done to ensure the safe return of Madeleine.

"We continue to work closely with the Portuguese authorities. They are very pleased with the collaboration with the British authorities.

"They are in close touch with Interpol and Europol and I know Kate and Gerry, with whom I have just been speaking, are very grateful for their efforts."

A British tourist claimed yesterday that two weeks ago she saw a man trying to steal a pushchair at the resort where Madeleine went missing.

Amanda Mills, 34, of Basildon, Essex, said that she reported the incident to police last week after reading about the girl's disappearance. "It was late at night," Mrs Mills said. "This guy came along and put his hands on a pushchair outside somebody's apartment. He didn’t even look to see if there was a child in it."

Portuguese police have told British officers that they believe the man who abducted Madeleine was a tourist from Britain or an expatriate linked to a network of paedophiles in the country.

Portugal is known to be a favoured destination for British paedophiles and the discovery in the early 1990s of a group of men who were abusing local boys helped to persuade the Government to make it illegal for Britons to have sex with underage children abroad.

Reports in Portugal have suggested that Madeleine, whose fourth birthday is on Saturday, had been "abducted for order". The Correio da Manha said: "One of the most substantial possibilities that the Policia Judiciaria is investigating is that this was paid for and commissioned by a international paedophile, probably of British origin."

Specialist detectives from the sex abuse and homicide unit in Lisbon were dispatched to the holiday region yesterday to take charge of the investigation after growing criticism that the police had been slow to react and had failed to make progress in tracking the abductor.

Antonio Santana Carlos, the Portuguese Ambassador in London, said that police were doing all they could but had to abide by the country’s secrecy laws. He said: "They are doing their best in cooperation with Europol and Interpol. For the parents of Madeleine McCann, we respect their suffering but unfortunately the investigation has to carry on in secrecy as that is in accordance with our laws." He added: "They have our understanding and we support them and we hope that soon there will be an end to their suffering."

Detectives have now ruled out a kidnap for ransom. There is nothing in the family history to suspect a revenge motive.

A source close to the police investigation told the 24 Horas newspaper: "Were it a kidnapping [for money] it would not be rational for someone to take on an almost 4-year-old when they could take one of the infants. It could be a kidnapping for sexual ends but one cannot exclude the possibility of the child having walked out and got lost and having fallen in a stream or a well."

Madeleine, from Rothley, near Leicester, disappeared when she was left with her brother and sister, 2-year-old twins Sean and Amelie, in a holiday flat. Her parents, Gerry and Kate, both 38, had been dining in a nearby restaurant and checking on them regularly.

Yesterday Mr McCann and his wife visited the Nossa Senhora da Luz (Our Lady of Light) Roman Catholic church, where they had taken Mass on Sunday, to pray privately for their daughter's return. Mrs McCann, a GP, was again clutching the Cuddle Cat that Madeleine took to bed.

Colleagues of the couple were offering prayers at Glenfield Hospital, in Leicester. About 300 people met at the hospital, where Mr McCann is a consultant cardiologist, at 1pm.

Villagers in Rothley held a silent vigil yesterday in a show of solidarity with the family. People were encouraged to light a candle or to tie a red ribbon around railings at the war memorial on the village green.

John Terry, the England and Chelsea footballer, with his colleague Paulo Ferreira joined Cristiano Ronaldo, the Portuguese international and Manchester United player, in making an appeal.

Terry said: "We are urging anyone out there with any information at all – please, please, please come forward. It's a terrible thing for her family to go through, she's only young so please, please come forward." Ferreira repeated the appeal in Portuguese.

Cuddle Cat

— The small soft toy that Madeleine McCann's mother, Kate, has been seen clutching is a favourite of her daughter’s

— The stuffed pink kitten is called Cuddle Cat and Madeleine hugs it when she goes to bed. She is also given the kitten when she feels scared or upset

— Since her disappearance, the soft toy has been all the more precious to her parents. On Sunday, before an emotional church service, Mrs McCann knelt kissing the toy’s head