In 12 of those cases, children were used to murder prisoners. Among them was Isa Dare, a four-year-old British boy, who was used to blow up a car in which alleged anti-Isil spies were trapped.

Child fighters are groomed from a young age that the caliphate is superior to any other nation. Violence and jihad are always present - for example, in counting lessons children tally up guns or tanks instead of apples or oranges.

Children are exposed to public executions and in some reported case encouraged to hold up decapitated heads or play football with them.

“The filming of such events is an attempt to promote the idea that the general public support executions. Children have been seen to eagerly seek a front row seat, demonstrating that they are not shy to watch such killings in public,” the report found.

The intensive grooming of children has parallels with both the Hitler Youth and Saddam Hussein’s Lion Cubs, the Ba’ath youth movement under the ousted Iraqi dictator. There are also parallels with the use of child soldiers in Liberia and Angola.

“Elements from Nazi Germany can be glimpsed in the systematic indoctrination of children through schools and training camps in [Isil], while abductions and forced recruitment employed by armies in Africa have been observed throughout Iraq and Syria,” the report found.

However, there are key differences. In most cases African child soldiers were abducted from their families and forced to fight, while Isil enlists radicalised parents to help indoctrinate the young.

“Mothers are given books instructing them how to bring up jihadi children, suggestions include telling bedtime stories about martyrdom, exposing children to graphic content through jihadi websites, and encouraging them to play sports and games which improve their fitness and hand-eye coordination,” the report found.

“In this way, children are brought up exposed to Islamic State ideology by those they trust and love, consequently making them more likely to trust Islamic State itself.”

Quilliam lays out suggestions for how indoctrinated Isil youth could be de-radicalised drawing partially on the lessons of demobilising child soldiers and of bringing young men out of gang culture.

Younger children who have not directly been involved in violence could hopefully be reintegrated into society fairly quickly with the help of counselling and debunking of jihadist ideology, the report suggests.

However, older children who were exposed to or involved in violence would require a much more intensive de-radicalisation programme.