That book could never exist. 1/20 and 1/100 for same event is a nonsense.
1/20 is 95% likelihood -if the book is over 100% bookies win. So even if had that and say 3 other candidates at say 10/1 (~10%) would be higher percentage than average book (~125%).
These articles are more on the money than Paul Hayward's piece I think.
http://www.espnfc.com/european-championship/74/blog/post/2891011/euro-2016-fan-clashes-at-england-vs-russia-match-troubling-sign
And also this highlight how unprovoked it was
https://www.theguardian.com/football/2016/jun/12/russian-hooligans-savage-organised-england-fans-marseille-euro-2016?CMP=share_btn_tw