Ch Supt Lea said the problems started when police baton-charged hundreds of Madrid fans out of the stadium.
Alfie Meadows, 21, of Brixton, south London, was allegedly hurt when he was struck on the head with a police baton.
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Mr Meadows, a Middlesex University philosophy student, had emergency brain surgery after he was allegedly hit with a police baton during the demonstration.
The officer is alleged to have - while on duty - repeatedly struck him on the body with his police baton to his injury.
Alfie Meadows sustained a brain injury when he was allegedly struck on the head with a police baton at the protest in central London on 9 December.
Negrin was so upset over the junk joke that he allegedly hit a co-worker in the parking lot with his (much larger and harder) police baton.
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Foreign television channels captured images of riot police baton-charging demonstrators.
After days of jokes about his small penis, Negrin confronted co-worker Hugo Osorno in the airport parking lot and beat him with a police baton, leaving him with bruises and abrasions.
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But some staff at the university accused the security forces of starting the violence, saying they believe the police baton-charged a group of students who had begun a planned march through the streets.
It is alleged that the officer, who was on duty, attacked Mr Alwan, a security guard at the nightclub, by repeatedly striking him on the body with his police baton to his injury.
The Independent Police Complaints Commission had been investigating the claim Mr Meadows was injured by a police baton, but the claim was suspended at the request of Mr Meadow's legal team after criminal proceedings were instigated.
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The Met Police is training more police to use baton rounds and is considering buying three water cannon.
The man he was fighting then appears to be struck repeatedly by a police officer wielding a baton.
All entry points to the proposed site were sealed off by baton-wielding police contingents stationed behind barbed wire.
Alternatives, such as using a baton or a police dog, often resulted in worse injuries than being Tasered, he added.
For example the police standard weapon - the baton - can be used, but only if its use is "proportionate to the level of threat".
Baton-wielding police officers broke up the rally.
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Police fired a number of plastic baton rounds as rival crowds of Catholics and Protestants clashed.
Flying pickets of mineworkers sent to stop deliveries leaving from mines were met by ranks of baton-wielding riot police.
They were climbing lamp posts, sitting on barbed-wire fences, standing on the roofs of cars and buses and some not fussed about getting a baton around the kneecaps by the police.
Other protesters tried to restrain the rioters but the violence spread and riot police moved in with tear gas and water cannon, making baton charges, as the rioters hurled stones and bottles.
Any police action against them, he said, would have involved a baton charge or the firing of tear gas.
They then sent in the police in the middle of the night to break up the fast, baton charge and tear gas the assembled supporters and evict the guru from the capital.
There were repeated baton charges, and after fires were lit on some of Paris' best-known boulevards, police used tear gas on the minority of protesters who were violent.
Nuala O'Loan, the police ombudsman, says that her investigations into routine (for Northern Ireland) events, such as the firing of baton rounds, have done more to establish a reputation for open-mindedness than have her inquiries into bombings, shootings and other enormities.
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