Prince William has been spotted doing undercover charity work in London

Prince William and Kate Middleton have returned to royal duties since the long bank holiday weekend celebrating the Queen's Platinum Jubilee. The royal family, along with the rest of the UK, marked the monarch's historic 70 year reign with a number of events including parades, parties and a live concert broadcast from Buckingham Palace.

While the Duke and Duchess of Cambridge are often photographed on official business, it seems that William was spotted doing some undercover charity work in London - and it has now gone viral.

LinkedIn user Matthew Gardner, a retired Met Police chief superintendent, shared a photo of his brother-in-law with William, explaining that he had been seen selling The Big Issue, a magazine and social enterprise which gives people experiencing homelessness the opportunity to earn an income.

Gardner wrote on the platform: 'My brother in law was in London today and saw a celebrity, so he took a photo at a distance. The celebrity saw the ‘covert surveillance’ effort and crossed the road to investigate further.'

He went on to say that it was, in fact, the future King.

'What an honour to have a private moment with our future King who was humble and working quietly in the background, helping the most needy. These ‘silent gestures’ often go unrecognised.

'The finale to this unique occasion was when Prince William asked my brother-in-law if he wanted to buy the ‘The Big Issue’, to which he replied ‘I have no change’.

'At this point William produced a mobile card machine… you cannot teach that ! Priceless, or should I say ‘Princely’.'

William was also spotted by cab driver Neil Kramer, who shared a photo of the royal on Instagram.

Kate Middleton also resumed royal duties yesterday after the Platinum Jubilee weekend, visiting Little Village baby banks which provide essentials to young children and families in need.