Hundreds of police officers are taking part in exercises to learn how to deal with a full-scale violent protest.
A first mock protest, involving 300 officers, took place at RAF Fairford in Gloucestershire on Wednesday night.
A second larger demonstration later, involving 170 "students" will include "flashpoints", allowing riot teams to test officers in live conditions.
Devon and Cornwall, Avon and Somerset, Wiltshire, Dorset and Gloucestershire police are taking part in the exercise.
The scenario for the first demonstration was set around two groups - played by officers - protesting over the building of a new mosque.
The aim was to give officers the opportunity to deal with an escalating level of hostility.
In Thursday's exercise, student volunteers will play the part of members of several fictitious pressure groups, protesting outside an incinerator under construction.
In each case, officers also had to minimise disruption to motorists and the local community.
Devon and Cornwall's Assistant Chief Constable Paul Netherton said: "We try to make it as realistic as possible.
"We have protesters, we have media, we have members of the public all playing a part in testing our officers."
Gloucestershire Police training specialist Insp Steve McGrory said such exercises were the best way to "simulate large-scale crowd control" and to test their ability to provide a co-ordinated response.
"The debriefing session after the exercise will tell us what we did right, and where we can improve our interoperability in the future," he said.
The Metropolitan Police were criticised during the G20 protests of April 2009 for being too "heavy-handed", and for not having enough officers to control crowds during the student fees demonstrations earlier this month.
Insp Steve McGrory said: "Large-scale riots are thankfully rare in Britain these days, but we would be failing in our duty to keep the public safe if we did not test ourselves in such challenging conditions."