A view of a street seen from a damaged balcony in the Khaldiyeh district in central HomsBy way of Andrew Roche LONDON (Reuters) – Britain said on Thursday it was once "very likely" the Syrian executive had used chemical weapons, and Turkey introduced it used to be stepping up testing of people fleeing the Syrian civil conflict for traces. U.S. Secretary of State John Kerry expressed gratitude to Russia for its willingness to check out to prepare a "Geneva two" convention to negotiate an finish to the struggle, in a sign of a thawing of the long diplomatic sit back between Washington and Moscow, Syria's strongest ally. …