The Queen walks with principlal Richard Backhouse during Berkhamsted School's 475th Anniversarty celebrations

A cousin of the Queen has revealed that he is gay and living with a man – with the full blessing of his ex-wife.

Lord Ivar Mountbatten, 53, is the most senior aristocrat of his generation, and the first in the extended Royal Family to come out.

The great-great-great grandson of Queen Victoria has found love with a Glaswegian flight attendant whom he met on a skiing holiday.

Lord Ivar, the son of the 3rd Marquess of Milford Haven, was previously married to Penny with whom he has three daughters. She is so supportive that she does yoga with his new boyfriend James Coyle and dines with the couple at their stately pile in Uffculme, Devon, at least once a week. The ex-couple have holidayed with their daughters and Mr Coyle in Verbier and spent last Christmas together as a family.

Lord Ivar’s family and friends, including Prince Edward, to whose elder child he is a godparent, are also thrilled for the great nephew of Earl Mountbatten of Burma. ‘Being a Mountbatten was never the problem, it was the generation into which I was born,’ Lord Ivar told The Mail on Sunday.

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‘When I was growing up, it was known as “the love that dare not speak its name”, but what’s amazing now is how far we have all come in terms of acceptance. I have struggled with my sexuality and in some ways I still do; it has been a real journey to reach this point.’

Lord Ivar married Penny in 1994 but he had known from his teens that he was bisexual. He revealed: ‘Penny was aware before we got married. I told her I was bisexual. She was understanding and I will always be grateful to her. We had a lot of fun, we have three fabulous daughters and I don’t regret any stage of my life.’

But his sexuality did eventually cause problems in their relationship, leading to their divorce in 2011, he said. ‘Ultimately, Penny did not feel sufficiently loved and she wanted more from a husband than she could get from me,’ he added.

He said he had a secret gay fling in 2014 but was not ready to admit his true sexuality, even to himself. That all changed when he met Mr Coyle, an airline cabin services director a year older than him.

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Mr Coyle said he takes his boyfriend’s family heritage in his stride, adding: ‘I called him from New York last Sunday night and he said he couldn’t talk to me because he was watching the ITV series Victoria. He rang back ten minutes later to say “my great-great-great grandparents have just got engaged, I can speak to you now”.’

Mr Coyle, who was brought up in a Catholic family in Glasgow, dated women before coming out in 2003. He insisted that his new boyfriend admit his sexuality, adding: ‘If I was going to be with him, it had to be in the open with friends and family.’ Lord Ivar added that his daughters were very supportive. He confided first in Ella, 20, who told him: ‘Paps, it’s no big deal,’ Alix, 18, discovered the truth when she read her sister’s diary, and he told Louise, now 14, when she was 12. They have accepted Mr Coyle, who has no children, as a father figure.

Lord Ivar said he was glad he had come out. ‘Now everyone in our family knows and could not be more supportive,’ he said.

‘In an ideal world, I know the girls would like their mother and father still to be together, but they love their 21st century family that we have built too.’