You appear to be claiming that McCann stories appear on the front pages of tabloids because they sell copy. You could only know that by comparing how many copies that are sold when there’s a McCann story on the front pages compared to when there isn’t.
Daily Express editor Peter Hill defends Madeleine McCann coverageSnipAt the time the Daily Express regarded the police as a credible source of information, he added. "I didn't know that they were behaving like tinpot Ruritanian idiots," Hill said.
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"I accept that we did libel Mr and Mrs McCann because under the law, we clearly didn't tell the truth about them," he said.
Madeleine McCann's disappearance generated huge amounts of public interest, with the Express receiving 10,000 messages a day about the story and its sales increasing by many thousands of copies each time an article about the missing child appeared on the front page, Hill added.
"You have got to remember that this was the most astonishing chain of events. Nothing comparable to this had been seen since the Lindberg kidnapping in 1932," he said.
https://www.theguardian.com/media/2009/apr/28/daily-express-peter-hill-mps