内容摘要：An official memo said social media vetting would be stepped up for student and foreign exchange visas, which would have "significant implications" for embassies and consulates.

An official memo said social media vetting would be stepped up for student and foreign exchange visas, which would have "significant implications" for embassies and consulates.

This week, with the weather pleasantly cool, hundreds of tourists are walking this trail, butall the tracks running north are closed off with police tape.

Because once again detectives are searching for clues as to what happened to Madeleine McCann, the three-year old British girl who went missing in May 2007, making the little seaside resort of Praia Da Luz famous for all the wrong reasons.Less than a mile from where she disappeared,press photographers with long lenses trying to get pictures are playing cat and mouse with officers from the Policia Judiciaria - the Portuguese equivalent of the FBI.

How can it be that 18 years on, this beauty spot dotted with ruined buildings, is being searched again? How was it not searched more thoroughly at the time?Madeleine's disappearance and the stories always accompanied by pictures of her with blonde hair and large eyes, have made news around the world for almost two decades now. But the story of the police investigations is a pitiful one.

When she first disappeared her parents struggled to get the Portuguese authorities to take it seriously, turning to the media to make appeals for anyone who might have seen her.

The apartment from which she vanished while her parents were having a meal at a nearby restaurant on the holiday complex was not properly sealed off, so vital forensic clues were lost.The 33-year-old has adopted three former service animals in total, including her current companion Marco, who served with Durham Constabulary for two years.

"It is the most rewarding thing having a retired police dog," she said.During his police service, Marco, now aged five, tracked a vulnerable man in a wood during the middle of the night.

"The man was wearing camouflage clothing and was unconscious when located laying face down under a bush," Ms Meller said."Without Marco, there was no way they would have found him given how dark it was and his camo clothing."