The Duke of Cambridge and his younger brother will mark the 12th anniversary of the September 11 attacks on the World Trade Centre and Pentagon by joining traders in London's Docklands to make big deals over the phone.
American global financial services company, BGC Partners, lost 658 employees on 9/11 and has hosted an annual fundraising event in their memory since 2005.
Overall, they have raised £56 million for charity.
Organisers are hoping this year will be no exception - all money generated will be donated to good causes, including SkillForce, of which William is patron, and WellChild, of which Harry is patron.
More top news
Plan would leave steelworkers worse off in retirement - but not as worse off as those in other pension schemes.
Donald Trump has labelled Hillary Clinton "crooked" and says he cannot wait to face her in November's US presidential election.
Thursday brings better temperatures