Writing in the journal Primary History, he said: “It is one thing to ask granny and grandpa to come into school and tell children about being evacuated and quite another to share with them the deep anxiety of leaving home.”

Professor Hayes said historical events could not be separated from their impact on people.

“In no other subject does such well-intended deceit take place,” he added.

“What sort of foundation is that to give our children?”

But Chris Davis, of the National Primary Headteachers’ Association, insists that young children are capable of hearing about unpleasant experiences.

“There’s violence and unpleasantness in fairy tales,” he said. “Children can cope with that kind of information. It’s unlikely to cause them trauma.

It would be a disaster to exclude all historical stories. Children lap up more at that age than at any other time.”

At five, children start learning about the lives of familiar people in the recent past, as well as famous people and events in the more distant past.

And the Qualifications and Curriculum Authority suggests that six-year-olds should be taught about the great fire of London, the Vikings and Florence Nightingale.

Professor Hayes said that, while primary teachers could use fictionalised stories to help pupils understand such topics, this must be converted into fact-based understanding by later teachers.

But he warned that: “This betrayal of innocence runs the risk of bewildering children as they suddenly become aware that much of what previously passed for history was a deliberately fictionalised and distorted account.”

Nicholas Tucker, a child psychologist, said: “Things have to be presented to children in child-like terms, otherwise they won’t understand them. They fill in the details later.”

Jacqui Dean, director of the Nuffield primary-history project, said:

“Children learn about history being a process of inquiry and build on that as they get older. Teachers can prevent misunderstandings if they teach well.”