The Royal Canadian Air Force are carrying out public duties in the UK for a month, including guarding landmarks around London.
In preparation for their time in Britain, personnel from across the Atlantic have been given vocal training to ensure their voices are in top condition when giving commands.
The voice clinic has been led by the Drum Major, Sergeant David Grenon:
"It goes back to the traditions of the military," he said.
"If you are in battle you actually have to scream to make sure that your orders go over the cannons and all the noise of the battle.
"When you're outside on a large field like it is at Buckingham Palace you want to make sure that all your troops will be able to hear all the different calls."
But how did Canadian personnel respond when instructed to respond only to Forces News reporter Lisa Hartle, and not Sergeant Donovan?
Royal Canadian Air Force personnel are in the UK until 15 July.