She is the former teenage pop sensation from Louisiana better known for her painful divorce and erratic behaviour than her music. But as America’s tarnished pop princess Britney Spears celebrated a triumphant comeback, sweeping the board at the MTV Video Music Awards on Sunday night, details emerged of a secret scandal buried in her family history that would have overshadowed even her well-publicised personal troubles.

Last week The Times traced the 26-year old singer’s ancestry back to Tottenham in North London where her great grandparents, George Anthony Portell and Lillian Esther Lewis, appear to have been living in sin before they were married - a major scandal back in the 1920s.

According to Parish records George, the son of a newsagent, and Lillian, daughter of a lighting inspector named James Lewis, were married on July 29, 1923 - the same day and at the same church, St John's Church in Tottenham, as Lillian’s sister Rose Florence Lewis. However, they gave the same home address on their marriage certificate, indicating they were already living together.

The insight into Spears’ background is just one of several extraordinary pieces of family history buried in the depths of the London Metropolitan Archives. That history will soon be available to internet users across the world at the mere tap of a mouse, under a plan to place the records of more than 77 million people online in one of the largest archiving projects ever attempted.

Laurence Ward, head of digital resources at the archives told The Times: “This is a goldmine that people have been waiting to get their hands on. It will allow them to find out more about history’s personalities, but also allow them to found out about their place in London’s history.”

Referring to Britney’s great grandparents Mr Ward said there could be an innocent explanation to the apparently scandalous family secret.

“Her great grandparents have certainly listed the same address in the records for their marriage,” he said.

“But as her great grandfather is recorded as being an able seaman, he may have been away with the Navy a lot. They could have recorded the same address as convenience. If they did live together before marriage, it would have been quite controversial for that time.”

The online archive - a joint project with Ancestry.co.uk - will include parish registers from more than 10,000 churches, containing records of baptisms, marriages and burials dating from the 1530s. Poor law documents, listing the inhabitants of workhouses, will also be included along with London school admissions and lists of convicts imported to the colonies.

From Charles Dickens to Vivienne Westwood, they contain the personal history of some of Britain’s most significant figures as well as ordinary Londoners and will be a major new resource for those trying to trace their own family history.

The increasingly popular pursuit has been boosted by television programmes such as Who do you think you are?, which has covered the family histories of celebrities including Patsy Kensit, Boris Johnson and Stephen Fry.

The archives also contain some fascinating pieces of social history. The Times viewed a bundle of divorce papers from a 17th Century adultery case.

Charles Bentley, esquire, wrote to his married mistress in 1720: “I should be glad to see you before Saturday but since I cannot enjoy so much happyness (sic), I wait until that day with as much patience as a lover can. I long to see you, what pleasure shall we partake of.”

Burial records at the parish of St Nicholas Deptford show exactly when the Great Plague of the 17th century began to take hold. While there were only a handful of deaths each month in early 1665, more than 100 were being recorded by the end of the year. The numbers continued to grow into 1666.

Josha Hanna, senior vice president of Ancestry.co.uk, said the records had “broad appeal and significance” to many people around the world.

The records will take about two years to place online because of their sheer number, as well as the significant preservation procedures needed for their handling.

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