Prince Harry's bromance with Barack Obama has fuelled rumours that the former US president and his wife Michelle will be top of the guest list when he marries Meghan Markle at Windsor Castle in May.

However, according to royal biographer Duncan Larcombe, it's extremely unlikely that the Obamas will get an invite as the couple will heed the advice of the Foreign Office not to do anything to upset diplomatic ties with the US.

Reports have suggested that the Foreign Office is nervous about upsetting current president Donald Trump, who has still not visited the UK in an official capacity or met the Queen.

Additionally, the royal family is supposed to remain neutral and above politics and no foreign heads of state were invited to Kate and William's wedding in 2011.

'There were religious leaders, members of the royal family, and commonwealth countries that were invited, 'he told townandcountry.com.

'I suspect that will be the same blueprint that Meghan and Harry will use. 'It’s all very carefully orchestrated to make sure that there’s no political overtones.'

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Despite their firm friendship Barack Obama will not be on the guest list for Prince Harry's wedding in May, as the couple take heed of Foreign Office advice not to upset diplomacy

Meghan and Harry have reportedly been urged by the Foreign Office not to make a 'political' statement with the guest list for their wedding

What might swing it for the Obamas is that Barack, 56, is, of course, no longer in office, and he and Harry, 33, do seem to have a genuine friendship.

Shortly after the engagement was announced, Mr Obama tweeted his congratulations to the couple.

He said: 'We wish you a lifetime of joy and happiness together.'

'I think part of their understanding is that Harry served as a soldier at the time when Obama was Commander-in-Chief,' Larcombe said. 'But there’s a different friendship there, rather than like a business relationship.'

Harry struck up a friendship with Michelle Obama, pictured at the Invictus Games in 2015, before he even met her husband

The royal interviewed the former President as part of his guest editing slot for BBC Radio 4's Today programme in December

The Foreign Office is eager not to upset Donald Trump who has not yet made an official visit to the UK or met the Queen

Harry himself dodged the question of whether Mr Obama will be on the guest list or not when quizzed about it during his guest editorship of the Today programme on BBC Radio 4

We haven’t put the invites or the guest list together yet, so who knows whether he’s going to be invited or not,” the British royal, 33, told BBC Radio 4’s Today programme when he guest edited the show on December 27.

'I wouldn’t want to ruin that surprise.'

Harry's special relationship with Barack and Michelle Obama Obama enjoyed a hugely successful state visit to the UK in 2011, when he and his family stayed with the Queen. Harry then struck up a rapport with Michelle Obama who he teamed up with on a number of initiatives, including offering his support to her campaigns for girls' education and better support for military families. But he didn't meet her husband until October 2015 when the royal visited the White House for a meeting to promote the Invictus Games. At the time, Obama warmly welcomed the prince, saying: 'I've had an opportunity to spend a lot of time with so many of his family members, but this is the first time that we had a chance to talk directly. Harry and Obama met for the first time during an interview at the Oval Office in October 2015 to promote the Invictus Games in Florida 'He has gotten to know Michelle very well, for a range of reasons, but in particular, he's here to talk about the Invictus Games, an initiative that is bringing together wounded warriors around the world, under the leadership of Prince Harry and others, to make sure that we see not simply the sacrifices they've made, but also the incredible contributions, strength and courage they continue to display.' 'And so we are very glad to support the Invictus Games. Michelle and myself are interested in promoting it.' When the Invictus Games was held in Florida last year the two men struck up a hilarious viral rivalry to publicise the competition, Harry playing the trump card by invoking his grandmother, the Queen to appear in a short 'skit' with him. There was another opportunity to catch up in April last year when Barack and Michelle joined William, Kate and Harry at Kensington Palace, where they met Prince George. The pair also attended this year's Invictus Games in Toronto this year, and were seen laughing together as they cheered on the athletes at the wheelchair basketball event. An onlooker even reported hearing the former president asking Harry about Meghan Markle and whether she was enjoying the games. The royal was one of the many high-profile guests at the former U.S. president's first Obama Foundation Summit in October. The 33-year-old was photographed sitting in the audience at the two-day event held at the Marriott Marquis McCormick Place in Chicago, Illinois one row behind Obama and his wife, former First Lady Michelle Obama. Prince Harry with the Obamas ahead of a dinner hosted by William and Kate at Kensington Palace in April 2016 Advertisement

However, Whitehall mandarins fear that by inviting Mr Obama and his wife Michelle it could be seen as a snub to Donald Trump.

President Trump has been highly critical of his predecessor and Government officials fear the thin-skinned billionaire might take offence if the Obamas receive a wedding invite and he does not.

Already there have been threats of mass protests if President Trump visits the UK in February to officially open the new US Embassy.

Meanwhile, Meghan previously made her dislike of Trump clear before he was elected suggesting she would move to Canada permanently if he entered the White House.

'It's really the moment that I go, we film Suits in Toronto and I might just stay in Canada,' she said during an interview on the Nightly Show with Larry Wilmore.

'Yes of course Trump is divisive. Think about just female voters alone.

'I think it was in 2012, the Republican Party lost the female vote by 12 points. That's a huge number and with as misogynistic as Trump is and so vocal about it, that's a huge chunk of it.'