According to this BBC article:
http://news.bbc.co.uk/1/hi/uk/8243176.stm
The whole operation was nearly screwed up by jumpy politicians. From the article:
The White House is suspected of putting pressure on the Pakistanis to arrest Rauf in 2006, which in turn forced the hands of the British, BBC defence correspondent Gordon Corera said.
Michael Clarke, director of defence think tank the Royal United Services Institute, said Rauf was picked up after the US secretly dispatched an envoy called Jose Rodriguez to Pakistan.
He told BBC Radio 4's Today programme: "The British were hopping mad about that because it meant... they had no alternative but to move in on this plot before all the evidence was as mature as possible.
"There is a general belief in British security circles that the dispatch of Rodriguez to Pakistan came straight from the White House."
Officers from Scotland Yard's Counter Terrorism Command had what they say was "good coverage" of the suspects and were waiting for more definite evidence before acting.
Scotland Yard's former head of specialist operations, Andy Hayman, said securing the arrests from a "standing start" after Rauf's arrest was a "very difficult challenge".
He told the BBC: "We couldn't gamble with the prospect that if the cell we were watching was alerted by that arrest, then all the things we'd built up along with other colleagues from the security services would have been lost potentially."
