Throughout the twists and turns of the hacking scandal, the constant aim of Downing Street has been to insulate the prime minister from the swirl of allegations that have engulfed some of his friends and political colleagues.
That task has become all the harder with the decision by Strathclyde Police to charge Andy Coulson with perjury.
For unlike the arrest of Mr Coulson last year by the London Metropolitan Police - which centred on claims about hacking during his time as editor of the News of the World - this arrest relates to a period when Mr Coulson was working as David Cameron's director of communications.
In other words, this was alleged wrongdoing committed while Mr Coulson was working inside Downing Street.
Inevitably the move will refuel arguments about the prime minister's judgement in employing Mr Coulson - and his initial decision to stand by him.
It also comes in the wake of charges being brought against two of Mr Cameron's friends - Rebekah Brooks, the former head of News International, and her husband Charlie Brooks.
And it is the day before the Culture Secretary Jeremy Hunt is to appear before the Leveson inquiry.
For Downing Street it makes shielding the prime minister from the hacking scandal fallout increasingly difficult.