The son of a former law lord has spent three times his inheritance on a failed bid to win a greater share of his father’s estate.

Michael Templeman (68) had challenged a revised will under which his father (Lord Templeman) left his £580,000 Devon home to his two stepdaughters.

In a previous will, Lord Templeman had bequeathed most of his £817,000 estate to Michael and his brother, Peter, with the sisters inheriting only £18,000 each.

Michael, a barrister, had argued that his father had been mentally incapable of amending his instructions because he had been suffering from dementia.

The High Court heard that in 1996 Lord Templeman married his second wife, Sheila Edworthy, and treated her daughters, Sarah and Jane, as his own. However, a family feud broke out when the former law lord died aged 94 in 2014.

Mr Justice Fancourt ruled that the revised will was valid and that Lord Templeman had wanted the sisters to inherit the house that had come to their stepfather after the death of his second wife in 2008.

“He had come to love them as if they were his own daughters and they him as if he were a father,” Mr Justice Fancourt told the court. “He left it to them because he felt, emotionally, that that was where [the house] belonged.”

The court heard Lord Templeman had decided to change his will after the death of his second wife. A new will was drafted and signed, leaving the property to Jane, 70, and Sarah, 66. His own sons would split most of the remainder of the estate.

The judge ordered Michael Templeman to pay the costs of the case, estimated at about £350,000 and more than three times his inheritance from his father’s amended will, The Times reports.

Michael had argued that his father did not have sufficient mental capacity to make the changes and that his stepsisters should inherit the £18,000 each they were due under the previous will.

However, Mr Justice Fancourt ruled: “There is no cogent evidence to suggest that Lord Templeman’s mental functioning was impaired in 2008 to any significant degree except in respect of the difficulty he was experiencing with his episodic memory.”