Censor.NET reports citing The Times.
As noted, Boris Johnson began his first day as foreign secretary pushing the idea of working with President Putin against ISIS in Syria and urging Britain to shrug off its "Cold War mentality." He changed his mind after a series of secret briefings by Foreign Office and military officials.
The briefings set out the rationale for Britain's policy of defeating ISIS while also supporting moderate opposition groups that sought the overthrow of Assad and that had been targeted by Russian bombs along with civilians.
One of the observations is thought to have included how the withdrawal of western support for the moderate opposition - including halting the supply of weapons - would spur radicalization and drive some into new alliances with Islamic State and al-Qaeda elements.
Mr. Johnson's turnaround since becoming foreign secretary has been dramatic. In December last year he advocated a British alliance with Assad and Putin "to remove the threat from ISIS. Everything else is secondary."
In his first phone call with his Russian counterpart in July, he spoke of the need to normalize relations with Russia. Since then he has taken a harder line, accusing Russia of "barbaric" war crimes in its bombardment of Aleppo. He has also criticized Russia for targeting western-backed rebels under the guise of striking ISIS, and said that Mr Assad had "no legitimacy" as Syria's leader.
Mr. Trump has embraced the idea of an alliance with Putin and Assad with even more enthusiasm than Mr. Johnson previously did. In an interview with the Wall Street Journal on Friday he indicated that would not change, adding that he was also likely to abandon efforts to arm and support the moderate opposition, saying: "We have no idea who these people are."
British officials hope that Trump's position may evolve once he starts receiving top-secret intelligence briefings about the intricacies of the conflict.
British diplomats are gearing up to persuade the incoming administration of the need to continue support for the moderate opposition and insist on Assad's departure.
"British policy on Syria has not changed because of a Trump victory," a Foreign Office source said.
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