Experts now understand Breivik was in a psychotic state during his killing spree that resulted in the deaths of 77 people and injured 151 on July 22

Their 243-page report will be reviewed by a panel from the Norwegian Board of Forensic Medicine.

At a media briefing, Norwegian prosecutor Svein Holden said it concluded that Breivik “is insane”.

Breivik, 32, is due to stand trial on 16 April for a hearing scheduled to last about 10 weeks.

He has admitted the killings but has pleaded not guilty to all charges. He remains adamant that that the attacks were atrocious but necessary for his campaign to defend Europe against a Muslim invasion.

The two psychiatrists who interviewed him 13 separate times have decided that he lived in his “own delusional universe where all his thoughts and acts are guided by his delusions”, prosecutors told reporters.