Sorry, watched one too many Malcolm Tucker clips on Youtube, one of which I sort of shamelessly borrowed from...

"Doctor, not that I don't appreciate it, but I've noticed over the course of our acquaintance that you don't ever swear, and I was wondering why that was." the Brigadier said as he walked with the Doctor down one of the streets of London where life was just beginning to return to normal following the whole incident with the dinosaur incursion.

"Galifreyans are only allowed a certain number of swearwords over the course their lifetimes, and if they go over, they're heavily fined for each offense." the Doctor replied. "I've been saving mine."

"Oh," the Brigadier replied. "Whatever for?"

"That." the Doctor replied, pointing to a grey-haired man in a blue suit whose coat had a red lining like that of the Doctor's favorite cape that was running towards a cab while a young woman in a short skirt trailed after him.

The cab drove off.

"Get the fuck back here!" the man yelled, running after the cab.

The cab stopped and the man and the young woman dove inside. The instant before it drove off, the Brigadier thought he heard the man say "Fucking drive off like that again, and I'll shove your fucking meter so far down your throat you'll be able to feel the price of your next shit!"