Anyone without a match ticket was not allowed in the main square. How they sorted that out I do not know.
Anyway, there were Merseyside police assisting the French. The Merseyside police identified a known hooligan and a drug dealer to the French as they were approaching the main square from a side street. The drug dealer was chased by plain clothes French police into the square, they caught and arrested him, some Everon started throwing bottles and so small uniformed squads were sent in to disperse fans from the centre of the square. They overreacted and misjudged the tear gas use but to them it may well have seemed there were scores or hundreds throwing bottles and they were few, sent in in small squads. The bleating about tear gas being used when children and families were around is typical as it's clearly OK for bottles to be thrown by our own without a single bleat about that scarring children or families for life nor infringing my human Ingurlish rights.
It was hardly World War 3 but let's face it the French wouldn't have been there if it was!
Ban Lille? It's always some other fucker's fault, to some.