I'm originally from the UK, so I've been reading and watching the news about the riots in London and the rest of the country. I was looking back over the list of riots on wikipedia at riots in the UK. There's been a pattern of rioting in the UK over the last thirty years. It seems during periods of recession, economic instability and periods of increased racial tension, there's more rioting.
I recall the riots in Moss Side in the 80's and also the Poll Tax riots in 1990. There was even a riot in Oxford of all places. The Poll Tax was an extremely unpopular tax implemented by the Thatcher Government. Sad to see the devastation in the UK. But if you are asking why now? If the history of rioting in the UK is anything to go by, economics has a big part to play. Not a justification, but certainly something to think about.
1979 - Southall Riots, (Southall, West London, England)
1980 - St Pauls riot, April 1980, (St Pauls, Bristol, England)
1981 - Brixton riot of 1981, (London, England)
1981 - Toxteth riots (Liverpool, England)
1981 - Moss Side riots (Manchester, England)
1981 - Chapeltown riot Leeds, West Yorkshire, England
1981 - First Handsworth Riot, (Birmingham, England)
1985 - Brixton riot of 1985, September 28, (London, England)
1985 - Second Handsworth Riot, September 11, (Birmingham, England)
1985 - Broadwater Farm Riot, Oct. 6, (London, England)
1987 - Chapeltown riot Leeds, West Yorkshire, England
1990 - Poll Tax Riots, (London)
1990 - Strangeways Prison Riot, (Manchester, UK), April 1 - April 25
1990 - Salford, (Greater Manchester, UK), July
1991 - Ely Petrol Riots in Cardiff, Wales
1991 - Carlton leach riot, Essex, England
1995 - Brixton riot of 1995, (London, England)
1995 - Hyde Park Riot, July 1995, Leeds, West Yorkshire
1995 - Manningham Riot, June 1995, (Bradford, West Yorkshire, UK)
2001 - Oldham Riots, May 2001, (Oldham, Greater Manchester, England)
2001 - Bradford Riot, July 2001, (Bradford, West Yorkshire, England)
2011 - Riots in London, Liverpool, Birmingham, Wolverhampton, Bristol, Nottingham, Manchester, Leicester, Gloucester, Chatham and Gillingham, England, at least 35 injured and 1 killed.