An officer from the Queen's personal guard has been caught on camera allegedly snorting a powder off a sword in St James's Palace, while on duty.
The footage, obtained by The Sun, shows one officer from the Coldstream Guards cutting lines with a plastic card, while another sniffs them.
The men have been identified by the Mirror as decorated Afghanistan and Iraq veteran Major James Coleby, and Captain Alex Ritchie.
The clip was accidentally posted on a messaging service for troops.
"The Army expects all personnel to stick to its high standards and any found to fall short are disciplined robustly," says the British Ministry of Defence. "An investigation is underway."