Ever since Who Do You Think You Are? first appeared on our screens in 2004, there’s been a growing interest in the roots of the rich and famous. From Boris Johnson’s unsurprising direct (but illegitimate) descent from George II to Jeremy Paxman weeping to learn of his Scottish great-grandmother’s abject poverty, it’s compelling to learn of people’s family backgrounds and see how they are as varied as our own. Some of the tabloids even employ their own teams of genealogists in order to dredge up secrets in the past as much as scandals in the present.

Politics is inevitably a field where tales from family history can provide titillating stories to confirm our prejudices of crookedness or lacking the common touch. During the last election, newspapers and websites fought to dig up details on all the party leaders, for example.

Everyone was delighted to learn that David Cameron is an eighth cousin of his archrival Boris Johnson (connected via another illegitimate line from George II), but it was also interesting to hear that his great-great-great-grandfather William Cameron was a farmer near Inverness – not so far from Gordon Brown’s farming roots in Fife. Equally compelling was Nick Clegg’s complex European ancestry: his grandmother was a Russian baroness, and his great aunt was Maria Zakrevskaya, a famed double agent for the Soviet Union and Britain who had affairs with both H G Wells and the Russian writer Maxim Gorky. On his more humble British side, his great-great-grandfather Simeon was a butcher in Leeds.

Meanwhile details of Labour leader Ed Miliband’s Marxist father were already well-known, but more fascinating is the story of his Polish mother Dobra Kozak’s escape from the Nazis as a child. She fled into hiding in a convent, losing her father and grandparents, and eventually escaped to England.

But what of the dark lord of politics, Peter Mandelson? Once again a senior politician has multinational roots. His maternal grandfather was Herbert Morrison, a humble policeman’s son and conscientious objector during World War One who went on to become a Labour cabinet minister in the 1940s and 1950s. But when the Daily Mail dug into Peter’s father’s Jewish roots, there were some interesting discoveries. His Polish great-great-grandfather Nathan Felthusen, born c1800, was a hero who fought for Russia against Napoleon. He later moved to England and changed his name to Mandelson, working as a baker (‘mandel’ being German for almond). The woman he married, Phoebe Cohen, had a distant connection to Nathan Mayer Rothschild, a founder of the banking dynasty, and to the family of Karl Marx.

And on the theme of Karl Marx… A German researcher, Hans Muller, was researching the life and family of Communist painter Carl Heinrich Pfänder (1819-1876), who was a close friend of Karl Marx and Friedrich Engels, only to discover that Pfänder was Victoria Beckham’s great-great-great-grandfather.

Another connection between a singer and a footballer was revealed when US singer Mariah Carey began digging into her roots. She believed there to be a connection to 1950s jazz singer Nat King Cole (not yet proven), but ended up discovering she is a distant cousin of English footballer Ashley Cole .

If British celebrities are hoping to find noble roots, many American ones seem to be keener to find humble ones. In 2008, billionaire Donald Trump arrived in his private jet on the Isle of Lewis in Scotland to visit the croft where his mother was born in 1912, daughter to a local fisherman. Microsoft founder Bill Gates has had his roots traced back 13 generations by genealogist David Glover to Halifax in Yorkshire. One of his forebears is believed to have been Jonas Halstead, a 17th century clothier’s son who sailed to Boston in 1635. Meanwhile Hillary Clinton is descended from a family of miners in Washington, County Durham. Her great-grandfather Jonathan Rodham came from Oxhill and emigrated to the coalfields of Pennsylvania in 1881.

Hollywood star Russell Crowe, who grew up in New Zealand and Australia, has everyday roots in Wales. His great-grandfather William Frederick Crowe was a greengrocer in Wrexham, and emigrated to Canada in 1925. His son Jack was left behind to run the family firm, failed to do a good job of it and headed for New Zealand. A few years ago the actor visited family sites in Wrexham as part of a BBC Wales documentary.

Many British actors have been revealed to have interesting roots. Philip Glenister, star of Ashes to Ashes and Hidden whose brother Robert is also an actor, is descended from the first chief constable of Hastings. William Montague Glenister (1828-1894) was a coachmaker’s son who joined the Metropolitan Police in 1843, became a detective at Paddington and then moved to Hastings. Many other members of the family have been documented at the one-name-study website www.glenister.org.

Another pair of acting brothers, Edward and James Fox, has some interesting heritage, too. Their maternal grandfather was dramatist Frederick Lonsdale, and their great-grandfather Samson Fox built the 1903 Royal Hall Theatre in Harrogate, one of the earliest buildings in the country to be made from concrete. Samson had risen from working in a textile mill as a child to becoming an inventor and philanthropist. Edward has recently helped to support the restoration of the theatre.

Actress Julie Christie, who was born in India, had a family secret only revealed in the last few years. A few years before she was born her father Frank St John Christie had an illegitimate daughter by one of his teenaged Indian plantation workers. Named June, she grew up separately when the family was torn apart by the discovery and the half-sisters were never reconciled. Keira Knightley turns out to be another actress with secrets in the family.

The Daily Mail discovered that her maternal grandmother Janet Williams unwittingly married a bigamist. John Gray, a lieutenant in the Queen’s Own Cameron Highlanders, was already married and was convicted of bigamy just six weeks after his and Janet’s son was born. The boy (Keira’s half-uncle) was given up for adoption and the paper eventually tracked him down to a council house in Bournemouth, not knowing of his famous connections.