The father of Ian Strachan has “washed his hands” of his son and denounced him for bringing shame on his family.

In his first detailed account of their strained relationship, Charlie Adalsteinsson says that his son abused his generosity by borrowing and never repaying thousands of pounds and traded on the family’s respected reputation.

The businessman, 52, says that Strachan, who adopted his mother’s maiden name, posed as a lawyer working for his great uncle, an Icelandic High Court judge, and ran up big bills at expensive hotels before fleeing without paying.

Only now can it be revealed that rather than being a socialite who mixed with royals, Strachan came from relatively humble beginnings and began his working life in a fish-and-chip shop.

In his father’s witness statement, which was not presented to court but has been seen by The Times, Mr Adalsteinsson says: “Paul has totally disrespected my family name and the name of my father. I come from a long line of decent men and there is no one in my family who would behave in the way he does.

“It appears that everything he does is for monetary gain with no thought to the hurt he causes. I have now washed my hands of him.”

Mr Adalsteinsson, who is from an Icelandic family and runs a fish business in northeast Scotland, said that three months after he married Elizabeth Strachan in 1976, Strachan was born. He was christened Paul Adalsteinsson and brought up in Aberdeen.

After six years, the couple separated and Miss Strachan took their two sons to America. When Strachan was 11, she returned and, according to her former husband, left her children with their grandparents in Scotland before going back to the US.

After attending Aberdeen Grammar School he became the manager of a fish-and-chip shop, although he pretended he ran a seafood restaurant. He later enrolled on a law access course at Edinburgh University before dropping out. He lost contact with his father, but rekindled their relationship after learning that his wealthy grandmother had died.

Mr Adalsteinsson, who had remarried, said: “He came to stay with us a couple of times. During this period he asked for money. Over time I gave him around £4,000.”

For Strachan, the lure of London was irresistible. He was determined to ingratiate himself with the capital’s wealthy. He posed as a journalist, a stylist and as a rich model and claimed to spend £15,000 a month on fine food, champagne and clothes. He lived with his mother, Elizabeth, in a three-bedroomed Chelsea apartment.

His father states that his son had run up a large bill in his latest “fraud”.

Times Recommends

• Milk: do we need a dairy godmother?
• DIY: the women doing it for themselves
• First double portrait of Princes unveiled