This week, gardaí searched an area in Boyle, Co Roscommon, in relation to the disappearance of Madeleine McCann. Their source? A psychic “tip-off” relayed to them by Interpol.

The result of the search? Nothing. Except to remind us that in any major disappearance or murder case, one thing is all too predictable: half the continent’s self-declared psychics and clairvoyants will insist on “helping”.

Investigating officers must steel themselves for the inevitable flood of calls from those with “visions” and “premonitions”. Offering a variety of certainties – that the victim is nearby, or far away; with two men, or three woman – they will drag the police from one fool’s errand to another.

“Psychics” swoop in on some promise of help, but have established only a record of hindrance. Already, the terrible case of Madeleine McCann – and the sizeable reward money on offer – has led Portuguese police to compile at least a couple of dossiers of “information” offered by so-called clairvoyants, psychics, fortune-tellers and assorted opportunists. At the start of June, Portugal’s Judicial Police made the error of admitting that they were following up on these, leading newspapers to claim, as the Daily Telegraph did, that investigators would “turn to mystics for help”.

In fact, they had done the only thing they could, which was to follow up each tenuous strand of information for fear that one might possibly be Madeleine’s abductor giving a disguised hint as to her whereabouts.

So the Portuguese police have had offers from the likes of Texan Brian Ladd, who claims to have drawn sketches based on a dream he had about a missing child. Obviously, this only came to light after the story had hit the headlines. Ladd then made a few more wild guesses, and produced some sketches for his website, which already includes all sorts of other dreams about nuclear attacks, plane crashes, the destruction of the Philippines and the following vision: “Soaking a golf ball in one’s own urine for 10 seconds will make the ball travel longer in the air, provided the person hitting the ball is the one whose urine is used. I do not play golf, and I’m not sure why I had this dream.” Philomena McCann, Madeleine’s aunt, reacted suitably. “It’s nonsense, there’s nothing in it. We must have had hundreds of things like that sent to us. We have been contacted by thousands of mediums from all over the world who claim to know something. There’s nothing in it.”

Some of those thousands have not confined themselves to working from home. The Portuguese resort from which Madeleine disappeared has since been busy with clairvoyants jetting in to lend their “powers” to the investigation.

They have included “psychic tracker” Amanda Hart who visited recently and declared that her vision included some people, mountains and a coastline, and a few countries: “I’m getting two locations now – Mombasa in Kenya (didn’t know Mombasa was in Kenya as got the names separately and found location on map) and either Amsterdam or Denmark.” How do we know that Hart went to Portugal? Because she employed a PR agency – on whose website you can read the unfolding narrative of Hart’s visions. The action, according to her “remote viewing”, has since moved to Lesotho and involves gangs and executions and plenty of other things that are unfolding in the fertile imagination of her crystal ball.

Most prolific is Diane Lazarus, the Welsh winner of Channel 5’s Britain’s Psychic Challenge and a woman with a lot of courses, CDs and books to sell. She has claimed to have helped in cases such as Jill Dando’s murder, although her website is a bit short on thank you notes from the relevant police forces.

She has also recently visited Portugal, concluding: “Quite honestly, I don’t think Madeleine has come to any harm.”

Lazarus has popped in on several high-profile cases, including some in Ireland, and often at the request of a desperate family member. According to a report in Dundalk paper the Argus, Lazarus arrived to assist in investigating the 2005 murder of Irene White. Police “looked into” her conclusions and found “nothing concrete”. Last year, Lazarus flew to Belfast to retrace the last steps of missing man Martin Kelly. He has yet to be found.

She also announced she would “find the Suffolk Strangler”, responsible for the deaths of five prostitutes in Ipswich last year. “I think he is a young lad,” she announced, “a hoodie, who, obviously, has no life.” Police later arrested and charged a 48-year-old forklift driver.

“It’s not always a blessing to have such a gift,” Lazarus has said. “It can be a curse at times.” She could be talking about any number of “psychics”.

Frustrated police, and some distraught families, know this more than anyone.