Prince Harry’s book “was horrible,” according to historian Simon Heffer, who warned the duke has since “lost his credibility.” The Duke of Sussex caused a stir when he released his memoir, Spare, last year that included a series of attacks on senior members of the Royal Family. Asked whether he had read the book, Heffer said: “I read bits of it. I mean, life’s too short, but I read enough of it to get a flavour of it. I thought it was horrible.” GB News host Steven Edginton asked: “Do you think that we should accept him back to the UK if Hollywood don’t want him?” He responded: “It’s not up to…