According to BBC's Laura Kuenssberg, the Tory party have owned up that neil wallis (arrested Friday, ex-deputy ed of NOTW), 'informally' advised Coulson (ex ed NOTW, also arrested), while Coulson worked for David Cameron in the run up to the election.
Odds on Cameron to be the next Minister to leave the Cabinet have shortened to 4/1. They were 100/1 a few weeks ago
EDIT: now 2/1 with Ladbrokes apparently.