The PM ordered the cash donation to military charity Fisher House to mark tonight’s annual Sun Military Awards.
It comes from a £35million pot of fines slapped on banks for the Libor rate-fix scandal.
All the cash is being doled out to military causes to help the traumatised or the needy.
The PM’s “Heroes Committee” of senior ministers and charity officials is deciding who will share the remaining £34million.
Mr Cameron told The Sun: “It took about two minutes for the Chancellor and I to decide what we wanted to do with the money from bankers who have been misbehaving. We wanted to know what more we could do for the wonderful people who serve our country.”
The PM — who will be at tonight’s star-studded Millies with wife Sam — added: “On the day that we will see some of the very best and bravest of our men and women at the Sun Military Awards, it is absolutely right that we continue to do everything possible to support our Forces, who are the very best of British.”

Fisher House, which is linked to the Help for Heroes charity, will use its cash to build houses for families so they can be close to loved ones in Birmingham’s Queen Elizabeth Hospital.
News International — The Sun’s parent company — recently gave £1.3million to Fisher House. The money came from sales of the final edition of the News of the World in July 2011.
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