Under intense pressure during a gruelling five-hour cross-examination by Andrew Green KC, for the Mirror, at the Rolls Building of the High Court in London, he admitted that his own book, Spare, contradicted one of his claims.

The Duke was also forced to concede that he had no idea how the Mirror journalists had obtained their stories, that he had “little to go on” and that he had not even read some of the articles that he alleged had caused him distress.

He admitted he was unaware that much of the information in the offending articles had already been published in rival newspapers and agreed that he could “see the similarities” between many of the stories.

Asked repeatedly what evidence he could offer to back up his phone-hacking claims, the Duke struggled to answer, insisting that such questions should be directed to the journalists who wrote the stories or even his own legal team.

“Are we not, Prince Harry, in the realms of total speculation?” asked Mr Green.

“You are the one who is bringing the claim so it’s perfectly legitimate to ask you.”

The Duke will return to court to face further questioning on Wednesday.

His UK visit is the first since last month’s Coronation, although it is unclear whether he will see any members of his family.

The King returned to London on Tuesday from a short, private break in Romania but is not expected to meet his younger son.

In his witness statement, the Duke revealed that he had spent years believing that the “numerous” stories focused on a rumour that James Hewitt, an Army Major, was his biological father, were designed to “oust” him from the Royal family.