The royal brothers attended the BGC Partners Charity Day where they were tasked with stepping into the shoes of traders for the day.
The Duke of Cambridge and his younger brother made their way to the trading floor to assist employees with sealing deals over the telephone. Judging by the buzz in the office and the excited looks on the brothers' faces, the royal duo seemed to have hit the jackpot.
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"Another trade secured by HRH The Duke of Cambridge here at #BGCCharityDay...," tweeted BGC Partners, alongside a photo of Prince William manning the phone.The first-time father was clearly getting into the swing of things as the morning drew on.
"HRH The Duke of Cambridge in the thick of the action #BGCCharityDay," wrote the financial company, next to a snapshot of Prince William negotiating a deal.
But it was Prince Harry who reportedly finalised the £21billion FOREX trade, a world record trade of its kind. The younger brother joked that Prince William, who recently welcomed the arrival of newborn Prince George in July, wasn't doing his job properly.
"He's on the phone and it's all baby chat," said Prince Harry, before turning to his older brother and saying, "Stop flirting, get on with it."
The younger royal had office employees entertained as he churned out technical language and pulled funny faces while gripping onto the phone.
The fundraising day was held in memory of the 658 employees of BGC Partners who died in the 9/11 attacks. The revenues from the day's trade will go to a number of charities including SkillForce, of which Prince William is a patron, and WellChild, of which Prince Harry is a patron.
Other celebrities who took part in the trading experience included Idris Elba, Thandie Newton Sean Bean and Rod Stewart.
The royal brothers have a busy day of engagements ahead of them. Straight after the charity event, Princes William and Harry rushed off to join their father at the funeral of Hugh van Cutsem, a close friend of Prince Charles.
Later in the day, new uncle Prince Harry will attend the annual WellChild Awards at The Dorchester Hotel on Park Lane. In 2007, Harry became a patron of the UK children's charity which is committed to ensuring that sick children have the very best possible quality of care.
The 28-year-old, who is often praised for his innate ability to connect with children, will present the award for "Most Inspirational Child" aged three to six and deliver a speech at the end of the ceremony.