Johanna van Haarlem looks across the Old Bailey courtroom to the hawk-featured man in the dock. There is no expression on his face. No remorse. And certainly no love.

For over 10 years, she had believed he was Erwin van Haarlem, the son she gave up for adoption as a baby in the chaos of Europe in World War Two. She'd embraced him into her family and showered him with all the love he'd missed as a child. Then she lost her son a second time when the police told her the man she now faced in court was an imposter. Apparently his real name was Vaclav Jelinek.

But Special Branch, MI5 and even the judge who sentenced Erwin van Haarlem to prison in 1989 as the last Soviet Bloc agent of the Cold War had no clue to his real identity - he was the spy with no name.

Using the name Erwin van Haarlem, he was ordered by his masters to spy on the Royal Family and the Labour Party, to infiltrate Jewish groups and plunder the West's nuclear secrets.

But his biggest betrayal was to the woman he tricked into believing she was his mother for more than a decade.

It was only after British intelligence caught the spy red-handed sending coded messages to Prague from his London flat that Johanna was finally forced to accept that the charming art dealer that she thought was Erwin was a professional liar. She had wanted so much to believe that he was her son that she had ignored one crucial clue that gave him away - his eyes were brown, and her baby's eyes were blue.