Police have arrested suspected con artists by creeping up on them in a double-decker bus.
Undercover officers from the Metropolitan Police commandeered a red London bus and pulled up alongside dozens of alleged gambling tricksters just yards from the Houses of Parliament.
The illegal gamers are said to target tourists on Westminster Bridge.
Officers made more than 12 arrests.
A Scotland Yard spokesman said: "By using the bus to arrive unseen and en masse officers were able to arrive right next to the suspects and quickly fill the area to prevent the suspects' escape and make at least 12 arrests."
Boris Johnson, the London Mayor, said: "We are rightly clamping down on the gangs of illegal gamers and thieves who can make visiting central London a misery."