Samantha Cameron visited Syrian refugees in Lebanon in March and is cited as the "biggest explanation" for the Prime Minister's stance over the conflict.
Sources close to Mr Cameron confirmed to the paper that his wife had pushed for a more robust response to the humanitarian crisis.
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The EC President said he welcomed a "more realistic tone" as he left discussions with Theresa May, but said more work had to be done.
Mild and a little bit muggy
The England cricketer will miss Wednesday's One-Day International against the West Indies after he was arrested in Bristol on Monday.