He described the intervention as ‘totally hopeless’.

Sources close to Buckingham Palace have denied that Boris Johnson was asked to give Prince Harry a “manly pep talk” to convince him not to step away from royal duties in January 2020.

The former prime minister claimed in his new book Unleashed that officials from the palace and Downing Street had asked him to intervene, which he described as “totally hopeless”.

However, sources familiar with these meetings have told The Telegraph that no such request as made.

This comes as Prince Harry made a surprise appearance on The Tonight Show with Jimmy Fallon as he visits New York alone for a series of philanthropic engagements.

Meanwhile, Princess of Wales has continued her gradual return to work after completing chemotherapy by visiting an “inspiring” ballet performance in London.

Kate, 42, later praised the performance on official Kensington Palace channels, where she described the performance of Giselle at Sadler’s Wells Theatre as “creativity at its best”.

Other upcoming engagements for the princess include the National Service of Remembrance in Whitehall and her annual Christmas carol service at Westminster, which she has already attended a meeting for.