Downing Street’s official denial that it played no behind-the-scenes role in the nine-hour detention of a Brazilian man at Heathrow airport was cast into doubt last night after a Washington official claimed the US was given a “heads-up” by the British government that “something was likely to occur”.

No 10 has so far refused to answer operational questions over the treatment of David Miranda, the partner of the Guardian journalist Glenn Greenwald, insisting that the decision to use UK anti-terror laws to question the Brazilian citizen had been taken by Scotland Yard.