Downing Street has offered a cautious welcome to Russia's withdrawal of troops from Syria, insisting that it will judge the move by evidence of developments on the ground.
Prime Minister David Cameron's official spokeswoman said that the move would be "welcome" if it signalled a new commitment to a genuine political transition in the war-torn Middle Eastern state.
Mr Cameron spoke with Vladimir Putin about Syria less than a fortnight ago, in a conference call with other European leaders, but Number 10 left no doubt that the Russian president's decision to pull troops out took Britain by surprise.
The international community was "not particularly expecting" the shift announced on Monday by Mr Putin, said the spokeswoman.
The president's declaration that action to shore up Syrian premier Bashar Assad had been successful was seemingly timed to coincide with a fresh round of peace talks in Geneva led by United Nations envoy Staffan de Mistura.
The PM's spokeswoman told a regular Westminster media briefing that Britain's focus was now on ensuring that the Geneva talks succeed.
Asked about Mr Putin's move, the PM's spokeswoman said: "If this signals a firm commitment by Russia to back genuine political transition, then it is welcome. But we will have to judge it by the action we see on the ground.
"As we stand here today, five years since this brutal civil war got under way - with 250,000 people killed and millions more displaced - it is a reminder of just how important it is that we reach a political solution in Syria that can pave the way for peace.
"We have tried many times in the past with the international community to make some progress, and therefore it underlines the importance of making sure that the process that de Mistura is leading now through the Geneva talks can really get us somewhere better for the Syrian people."