A claim by my fellow Mail columnist Craig Brown earlier this year that Queen Elizabeth found Donald Trump rude led him to insist that he was, in fact, ‘her favourite president’.

Now, however, I can confirm that our late monarch did indeed find the US president-elect disrespectful – and reveal what caused the offence.

A source involved in arranging Trump’s 2018 visit to this country with his wife, Melania, tells me that the tycoon made a comment about the Queen’s sister, Princess Margaret, who died in 2002 aged 71.

‘Trump put his foot in it by saying Margaret must have been a difficult sister,’ the source tells me. ‘The Queen was very annoyed with this remark, which she viewed as ignorant and hurtful. She always defended Margaret to the hilt.’

It’s not clear why Trump made the alleged comment but he may have prepared for his visit by watching Netflix hit The Crown, which portrayed Margaret as rebellious, volatile and resentful of her elder sister.

In the two series aired before Trump’s visit, Margaret’s decision not to marry Peter Townsend featured heavily, with the Queen and her government shown opposing her desire to marry the divorced Group Captain flying ace, which would have required the monarch’s permission under the Royal Marriages Act 1772. 

In reality, a plan was made to amend the Act to allow the marriage while removing Margaret and her children from the line of succession.

Craig Brown’s book, titled A Voyage Around The Queen, claims that the late sovereign had confided in a guest that she had ‘particularly disliked’ the way Trump looked over her shoulder as if ‘in search of others more interesting’.

She is also said to have mused that he ‘must have some sort of arrangement’ with his wife after hosting him during one of his two visits.

Trump said the comments were ‘totally false’. He told the Mail: ‘I heard I was her favourite president. I had a great relationship with the Queen. She liked me and I liked her. She was an amazing woman.’