Presenter: So Tom, are we really surrounded by secret societies? And are they indeed so popular among young people, especially those at famous universities like Yale or Harvard in the States, or Oxford and Cambridge here in Britain? Could you let us in on some of the secrets?

Tom: [Manchester accent] Well, we know that secret societies exist, and that many public figures have belonged, and might still belong to them. And, yes, it's often the case that people join a secret society at university. For example, David Cameron, the young Conservative leader, was in the Bullingdon Club at Oxford. Prince Charles was a Cambridge Apostle when he was there … And university societies like these are particularly popular in the States – they call them fraternities, or ‘frats' – and sororities if they're just for women.

Presenter: Like the famous Gamma Phi Beta society?

Tom: Exactly. Broadly speaking, most of these organisations have names made up of Greek letters, which have a ‘secret meaning' that only members know. And they tend to have lots of secret rituals and symbols, like passwords, songs, handshakes, initiation rites, that sort of thing.

Presenter: And don't they all live in the same place as a rule? In a ‘frat house'? You see it in movies sometimes.

Tom: Oh yes – that's important. It's to encourage members to ‘bond', to develop a special relationship with each other. And also to provide a kind of centre for events, administration and so on.

Presenter: Is it hard to become a member of one of these organisations?

Tom: Well, they have what's called ‘Rush Week', when new students are invited to meet members of the different frats. Each one has different requirements, such as a minimum grade average. Then at the end of the week, the house invites some of the students to ‘pledge' to the fraternity or sorority.

Presenter: And are these organisations very influential beyond university, Tom?

Tom: Well, it's widely believed that they are. Many of their members have gone on to be very successful in life. For example, one Yale University fraternity, Delta Kappa Epsilon, had six members who went on to become President of the United States!

Presenter: Really? That's incredible. So do members usually keep in touch after they leave university?

Tom: There's a common belief that many of them do …But we can't be sure, can we, because it's all a secret!

Presenter: Exactly.