Prince William just ditched his royal title for a very special reason

He simply signed the letter 'William'.

They may have managed to sneak in a secret holiday to the Isles of Scilly earlier this month, but the Duke and Duchess of Cambridge are fully back in work mode following their well-earned summer break.

Between Kate's rumoured impending royal promotion to Princess of Wales, and the couple's back-to-school prep for Prince George and Princess Charlotte, it's been a busy few weeks in the Cambridge household – and it's only likely to get busier.

But amid a packed schedule of routine royal duties and end of summer family time, Prince William has taken some time out to a pen an important letter of support to a former Royal Marine who tragically lost his home in an arson attack earlier this year.

Sean Ivey, who received the letter from the prince praising his "moral courage to stand up for what is right", believes his home was targeted due to his stance on anti-social behaviour in his local area.

"For a person to be put in such a position, simply due to having the moral courage to stand up for what is right, is reprehensible; I stand beside you," the prince wrote, adding how "heartened" he was by a public appeal to support Sean and his family, which received over £300,000.

But there was one very special aspect of the letter that left the marine particularly surprised: the Prince had dropped his royal title and simply signed the down-to-earth letter 'William'.

"It hasn't even got Prince William or His Royal Highness Prince William of Duke of Cambridge, it's just William. He recognises the problem and I'm honoured he's said that," Ivey, who has previously served in Afghanistan and Iraq, told the BBC.

While those behind the fire have not been found – with Ivey's case dropped by police back in May – the marine is now planning to set up a charity for young people in his neighbourhood.

"If our own royal family are recognising this problem in our society, other powers that be should take more swift action to eradicate it," he added.

It's set to be a significant week for both Princes William and Harry, as they mark the 24th anniversary of their mother's death on Tuesday.

While it's been announced that the specially-commissioned statue paying tribute to Princess Diana in the gardens of Kensington Palace will be granting special access to members of the public wishing to pay their respects on the day, it's thought that both princes will mark the anniversary privately.