David Howells, 48, was not present when his wife was killed but Mr Justice Alliott condemned him as the instigator of the crime, and his recommendation to the Home Secretary on the minimum jail term to be served would take account of that. Recommendations on the boys would reflect that Glenn, 17, who repeatedly struck his mother with a hammer, was the actual killer. John, 16, who disposed of the murder weapon and his brother's bloodstained clothes, had an "active if less crucial" role, the judge said.
A jury decided on Tuesday that the father and sons had plotted the killing together after the boys suffered years of abuse from the history and religious affairs teacher. Mr Justice Alliott then took the unusual course of giving the three 24 hours to confess the exact roles they had played before deciding what tariffs to recommend. "I don't know the whole truth," he said.
The period of reflection resulted in Glenn Howells admitting for the first time that his father had been involved in discussions about killing his mother in a mock burglary - but David Howells persisted in denying active involvement.
Gary Burrell QC, acting for Glenn, told the court: "The reality is that none of us will ever know the full story." But Glenn should be sentenced on the basis that the killing, in August 1995, "would never have taken place without David Howells' prior approval, without his prior knowledge, and without some, implicit at least, encouragement."
Simon Hawkesworth QC, counsel for David Howells, said Mr Howells denied active complicity in any plan to kill his wife. "He does accept, as he must, that he failed to act to prevent this tragedy and that it was in his power to do so. To that extent he recognises that in his role as father, he failed his sons and there's a heavy moral responsibility."
But the judge told him that he had led his sons into doing what they did. "There cannot be anything more vile than to get your sons to kill their mother, unless it can be to confront cheerfully their long detention while you went free.
"Yours is by far the greatest culpability and I shall reflect that in my recommendation." The father was playing a pub darts match when the murder was carried out, enabling him to put forward an alibi defence in court.
Aiden Marran QC, acting for John, said the younger son had been damaged by the bizarre behaviour of his mother, but there was also a sinister element - his father. John's increasing isolation and desolation had led him to rely and depend more and more heavily on his father.
Mr Marran called a consultant forensic psychiatrist, Dr Peter Wood, who told the court that John had become significantly behaviourally disturbed by his mother's behaviour and "chronically dependent" on his brother and father.
From the time John was 10, a fantasy had begun of how the boys might achieve a "life without mum", and they began to think about causing her death. The ideas had become firmer as time went on.
"In a positive way, and later more actively, his father did not discourage him and later probably encouraged him to find a radical solution to their problems. It was an unbalanced situation and as the youngest member of the family, John was very vulnerable," Dr Wood said.Reuse content