Royal expert says Prince Harry was a 'mischievous' child and his freedom would 'irritate' Prince William

When Prince William and Prince Harry were young children, much was made of the brothers being 'an heir and a spare' which is something that Princess Margaret reportedly also struggled with as Queen Elizabeth II's sister. Insiders have also spoken about the difficulties Prince George - who is third in line to the throne - and his siblings, Princess Charlotte and Prince Louis, will face as he grows older and follows a different royal path.

However, one royal expert has claimed that while the focus on William one day becoming King left Harry feeling overshadowed, it also allowed him more freedom than his older brother - and that this would sometimes 'irritate' the now Duke of Cambridge.

In Robert Jobson's new book, William At 40: The Making Of A Modern Monarch, he discusses Harry's 'mischievous' side and claims that his cheeky nature was encouraged by the late Princess Diana.

In extracts published in the Daily Mail, the author writes about a time when royal protection officer Ken Wharfe reportedly heard the brothers arguing in the car, with Harry saying: 'You'll be King. I won't - so I can do what I want!'

Jobson writes: 'Certainly, Harry seemed to revel in the freedom that he knew William would never have. He was far more mischievous — and sometimes totally out of control.'

He added that William was 'also capable of wild behaviour' but would become 'irritated' by Harry.

Discussing how Diana handled her sons, Jobson continued: 'The truth is that the princess actively encouraged Harry’s mischievous nature, which was in some ways akin to her own.'

She reportedly found their antics 'hilarious' and 'believed in letting her boys run wild and free'.

Harry recently discussed how he feels his mother's presence 'in everything [he] does', and William often speaks about how he keeps her memory alive with his three little ones.