Ronald Darwin said his son had "respectable" jobs as a bank worker, science teacher and prison officer.

But the 90-year-old added: "I don't know what has happened to him."

Widower Ronald, increasingly frail since a stroke 21 years ago, was stunned but thrilled when his son returned home after being missing for five years.

But his elation turned to horror when John was arrested and discovered he had been cruelly deceived.

As details emerged, the war veteran told of his fears his eldest son always had "ideas above his station".

Ronald said: "Years ago he said 'I'm going to buy a big farmhouse in Scotland and breed cattle' but he never did. He had big dreams and ambitions. He wanted to be a flying officer at one time though he never did any training for it. I sometimes think he was in a bit too much of a hurry to make money."

John Darwin's aunt Margaret Burns, 80, who lives near Ronald, in Blackhall Colliery, said she was stunned by the revelations and furious at the hurt he had caused his dad.

Margaret Burns said her nephew had only once made contact with his father in the past 36 years, and that was on the day of his mother's funeral 16 years previous, and predicted he would be a millionaire by the age of 50.