When he was 20, says Strictly Come Dancing judge Len Goodman at the start of his episode of Who Do You Think You Are?, he couldn’t have given a “monkey’s armpit” about his family history. The former welder, who took up ballroom dancing because it was a way to meet girls, has changed his mind and wants to learn more about his forebears.

His first stop is Bethnal Green in London’s East End, where Len was brought up. “Doors were never locked, it was lovely, it was a true community,” he remembers. On a visit to his stepmother, Irene, where he’s joined by son James, Len sees old photographs and his grandparents' marriage certificate.

It’s enough information for Len to start to follow his maternal grandfather’s family line through census records. These reveal that his great grandfather, Thomas, was a bricklayer who had at least eight children. “This is what you got when there was no TV or radio,” quips Len. Going back another generation, the census shows Thomas’s parents, James Eldridge and his wife Sarah, living with 11 children.

But what was life like for them? Tough, suggests a meeting with Sue Donnelly, an archivist who looks after the Charles Booth collection. Booth was a Victorian social researcher and philanthropist who mapped London according to the living conditions of its inhabitants. In the middle of the 19th century, Bethnal Green was an area of huge poverty. It was also overcrowded, in part because so much housing was knocked down in the 1840s to make way for the railways.

A story of one of Len’s forebears brings the conditions all too vividly alive. In 1889, as an old newspaper report reveals, James committed suicide rather than be sent to Bethnal Green’s notorious workhouse. Even when Len was a child, he remembers, the family had a “morbid fear” of the workhouse.

Further research suggests the fear may have been well founded. John Cecil, James Eldridge’s father-in-law, ended his days in Bethnal’s workhouse, dying of asthma in 1866. It’s a story given added poignancy by the fact that John was once a prosperous man, a silk weaver whose father, Daniel, left him property. Sadly, the decline of the silk industry in the 19th century meant that John lost both his livelihood and his inheritance.

Next, Len wants to research the life of his 2x great grandfather, Josef Sosnowski, who came to Britain in February 1834. In a Portsmouth cemetery, he sees a memorial to Josef as one of a group of 212 Polish soldiers who fetched up in the city aboard a ship called Marianne. But what were the circumstances around the men coming to the UK?

In Poland, Len discovers more. Josef was a member of a crack cavalry unit that fought in an uprising against Russia, which controlled much of modern Poland in the early 19th century. Honoured for his bravery on the battlefield during the November Uprising of 1830-31, Josef was eventually forced to flee his homeland for Prussia when the rebellion was crushed.

Expelled from Prussia after being “cruelly beaten up” and enduring more than a year of imprisonment in terrible conditions, Josef was on his way to North America when a storm forced the Marianne to take shelter on the south coast. In Paris,where many records relating to Polish exiles from this era are kept, Len learns that Josef was active in politics in such organisations as the Polish Society, which campaigned for Polish independence. Later in life, Josef knew Karl Marx.

“I feel no different, I look no different, I am no different and yet I’m not what I thought I was,” says Len. “I thought that I was truly an Anglo-Saxon, English through and through.” Despite the struggles endured by his forebears, he’s delighted with what he’s learnt.