It started with a suitcase hidden under a bed.

It was 2009, and Antony Easton's father, Peter, had recently died. As Antony started to engage with the messy business of probate, he came across a small brown leather case in his father's old flat in the Hampshire town of Lymington.

Inside were immaculate German bank notes, photo albums, envelopes full of notes recording different chapters of his life - and a birth certificate.

Peter Roderick Easton, who had prided himself on his "Englishness" (and been an Anglican) had, in fact, been born and raised in pre-war Germany as Peter Hans Rudolf Eisner, a member of one of the wealthiest Jewish families in Berlin.

Despite hints about his father's origins growing up, the contents of the suitcase shone a light into a past that Antony knew almost nothing about. The revelations would lead him on a decade-long trail, revealing a family devastated by the Holocaust, a vanished fortune worth billions of pounds and a legacy of artwork and property stolen under Nazi rule.

Black-and-white photographs gave a glimpse of Peter's early life, far removed from his son's modest upbringing in London - they showed a chauffeur-driven Mercedes, mansions staffed by servants, staircases ornately carved with angels.

More ominously, one picture showed 12-year-old Peter Eisner smiling with friends, a Nazi flag rippling in the distance.

"I felt it was a hand reaching out from the past," says Antony.

He says his father was a quiet and serious man, if prone to bouts of anger. He avoided talking about his childhood and always shut down questions about his slight German accent.

"There were clues that [he wasn't] really like other people… There was a darkness around his world," says Antony.

The next big clue about Antony's family history came from a work of art.

Enlisting the help of a friend who spoke fluent German, he asked her to dig into a company called Hahn'sche Werke, references to which were peppered among the documents in the suitcase. After searching online, she sent Antony a photo of a painting, depicting the inside of a large steelworks - seemingly owned by the business

Molten metal glows hot on a conveyor belt, illuminating the faces of busy and attentive workers. It is an image of industrial power and might, from an era when Germany was hurtling towards decades of devastating war.

The 1910 painting, by the artist Hans Baluschek, was called Eisenwalzwerk (Iron Rolling Mill). It had been owned, and was likely commissioned by Heinrich Eisner, who had helped build the Hahn'sche Werke steel business into one of the most high-tech and sprawling companies in central Europe. The documents in the suitcase showed that this was Antony's great-grandfather.

More research revealed that, at the turn of the 20th Century, Heinrich was one of the wealthiest businessmen in Germany - the equivalent of a modern multi-billionaire.

His company manufactured tubular steel, with factories spread across Germany, Poland and Russia.

Heinrich, and his wife, Olga, owned several properties in and around Berlin, including an impressive six-storey property in the city centre with marble floors and a cream-white facade.

A photograph from the early 1900s shows a man with a softly rounded belly and a straight white moustache. Heinrich wears a black suit, and Olga sits next........

© BBC