The Metropolitan Police have raised the possibility of using water cannon on crowds in London if violence breaks out at demonstrations.
Calls for the deployment of water cannon were sparked by violence at last Thursday's protest against the planned hike in university tuition fees, including an attack on a car carrying the Prince of Wales and Duchess of Cornwall.
Following speculation that Camilla was struck by a stick pushed through the window of the royal couple's car, Home Secretary Theresa May today confirmed that "there was some contact made".
And she announced that an urgent police review of royal security will be completed by December 17, though it was likely that few of its details will be made public.
In a statement to the House of Commons, Mrs May said that police believe "organised thugs" - some armed with snooker balls, flares, fireworks and stones - had infiltrated last week's student protest.
With more protests expected this week when the House of Lords debates the increase in the maximum tuition fee to £9,000 a year, Scotland Yard said it had no current plans to deploy water cannon but would not rule out their future use.
The head of the Met's public order branch, Commander Bob Broadhurst, said: "There are no current plans to use water cannons on the streets of the capital but we would be foolish if we did not take time to look at tactics such as this to see if it might be appropriate in the future.
"I would emphasise we will not rush in to anything and we are not in the business of knee jerk reactions.
"Anything we do will be carefully and fully considered to ensure the best outcome for protesters, officers and all Londoners."