Tatham has never been back to the US, where she had left behind friends, a flat and a job.

BBC: Dame Margot Fonteyn and the Panama sanitary towel coup

"The site has really just rocketed, " said Matt Tatham, another spokesman from Experian.

CNN: Report: Pinterest is third most-visited social site

"I was shovelled out of the plane by the pilot's door, while she went out to face the press, " Tatham recalls.

BBC: Dame Margot Fonteyn and the Panama sanitary towel coup

Mike Lanchin interviewed Judy Tatham for the BBC World Service programme Witness.

BBC: Dame Margot Fonteyn and the Panama sanitary towel coup

And once again, Tatham says she did not want to intrude.

BBC: Dame Margot Fonteyn and the Panama sanitary towel coup

With the help of embassy staff, the ballerina was freed from custody and put on a plane to the US. She called Tatham from the airport.

BBC: Dame Margot Fonteyn and the Panama sanitary towel coup

One caveat: Since the data doesn't include mobile traffic, sites such as Twitter, which sees much of its traffic from smartphones and tablets, may take a hit in this ranking, Tatham said.

CNN: Report: Pinterest is third most-visited social site