The latest allegations about the extent of British and US spying are fuelling the debate about surveillance - with reform of the US National Security Agency appearing inevitable.
President Barack Obama told a press conference that "trust had been diminished" and it was important to take that into account when weighting up how the US "structures these programmes."
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The Prime Minister will urge leaders of the other 27 EU states to move on as quickly as possible to talks on Britain's future trade.
Despite temperatures reaching double figures in the south today, it was still a chilly day, with brisk winds.
The four-time Tour de France winner has said he has always taken great care to stay within the rules after returning an adverse urine test.