David Cameron said Syria's "history is being written in the blood of her people" and added that there was an "urgent window of opportunity" to deal with the crisis before our "worst fears are realised."
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Heavy downpours have triggered flash floods in Yorkshire.
The IMF's forecast for global growth has been cut to 3.1% - a fifth successive year of declining growth, the weakest performance since 2009.
Coronation Street actor Ryan Thomas is to quit the show after more than 15 years.