The Metropolitan Police Commissioner, Sir Paul Stephenson, says a detailed investigation has begun into violent protests against a rise in university tuition fees in England.
These two students were in London, peacefully taking part in the protests.
Here they describe what they saw, and share their video footage of events:
A-level student Jonathan, from Hampshire
The royals need to increase their intelligence and information - they should have known that there was a large body of agitated protesters in the area and they should not have tried to drive the car down the street.
I can't understand why they drove down there - Regent Street was completely clogged. I'd seen people throwing bins and knocking things over.
At one point a traffic cone came out of nowhere and was thrown with such force that it knocked over a policeman.
He went down like a sack of bricks - he was really dazed. My aunt and I stood in between the crowds and the policeman on the floor trying to help him up. Then a bar owner came out and helped the policeman inside.
Earlier in Parliament Square I had seen groups of people coming back from the front covered in blood.
Graphic design student Joshua Coombs, from Kent
I was standing on a wall that protects the building in Parliament Square, from where I was filming.
There were about 10 people throwing bricks and smashing windows.
This video shows one person attacking a window.
Some others were using the breeze blocks that hold up the fences in the area - they were using anything.
Then the police came along and cleared the students away from the area around the building.
I thought it was utterly pointless and gives students a bad name. I think the protests were irrelevant - the bill was always going to go through anyway.