12:04 BST
Tom Little KC, prosecuting, told the hearing at the Court of Appeal in central London: “What the facts reveal is a case which, on any view, was exceptional, even in the context of a murder.”
He argued a whole-life order would be a “just punishment” for Nicholas Prosper, who has been watching proceedings via a video link to him at HMP Belmarsh in Woolwich in south-east London.
The prosecutor continued: “It was a murder of three people, two of them were children, including the intended rape of the sister. That did not take place, but it had been intended.”
The barrister for Prosper told judges that the sentence, with its 49-year minimum term, “cannot be said to be unduly lenient”.
David Bentley KC, for Prosper, said: “The reality is that with the existing sentence, the earliest date he could actually be considered for parole is in his late 60s, and the dangerousness is covered by the life sentence.”
The judges said they had hoped to reveal their decision from 12:00.