I don't often feel like praising David Davis, but credit where credit's due - he's just given an excellent interview on the Today Programme on why he is opposing Labour's plan to double detention without trial to 56 days. So forceful was he that he barely allowed the interviewer - John Humphrys of all people - to get a word in edgeways!

It helps, of course, when you have the facts on your side. He's quite right that the Government already have powers to declare a state of emergency if they want to question people for longer than 28 days - and if they want to do that, it better bloody well be an emergency! And as to the Government's motives? Simple Sailor West's remarkable turnaround from

"I still need to be fully convinced that we absolutely need more than 28 days and I also need to be convinced what is the best way of doing that."

to

"I am quite clear that the greater complexities of terrorist plots will mean that we will need the power to detain certain individuals for more than 28 days."

after doing no more than a brief chinwag with Gordon offers a clue. Davis again is on the money - West is an undoubted expert in this field, so what evidence could Brown possibly have provided that he didn't know already? Instead this illustrates precisely what we all suspected - that the motives for this proposed extension are entirely political.

As I say, I don't often praise Davis but whatever you think of his politics, his calibre as a debater is undoubted - and on this and the ID cards issue I often find myself glad that he's on our side.