British Prime Minister David Cameron's former spokesman Andy Coulson, once the editor of Rupert Murdoch's News of the World, found himself in police custody for a second time on Wednesday, in a perjury case. 

The Guardian's Severin Carrell has the details: Police came to Coulson's London home at 6:30 a.m. on Wednesday and drove him to Glasgow, where he's to be questioned for allegedly perjuring himself in 2010 trial of Scottish socialist politician Tommy Sheridan, who was also charged with perjury. Police suspect Coulson of misrepresenting what he knew about News investigator Glenn Mulcaire targetting Sheridan and his family with illegal hacking.

The detention has potentially disastrous implications for Cameron, as Reuters' Kate Holton and Tim Castle explain: "it calls into question his judgment in seeking to win Murdoch's backing by employing one of his most powerful journalists." Write Holton and Castle:

"This simply reinforces the questions that are hanging over the prime minister about his judgment in appointing Andy Coulson in the first place," said Ivor Gaber, professor of political journalism at City University in London.

"We now know that lots of people warned Cameron that this might not be an appropriate move," he added.

Coulson has already been arrested once, last July, for corruption and phone hacking, so he knows this drill.