The Sketch: When a professional decision is designed to conceal political betrayal

These evidence sessions for the new Public Bill committees – they might be a great adornment to the process. That's most unusual for innovation. "What do we need change for, aren't things bad enough already?" as the great Conservative adage had it, in the days of real financial stability (1815-1914).

The Counter-Terror Bill is written and under scrutiny; witnesses from the world outside come in to be examined on the detail. Here we have the proposal to extend detention without charge to 42 days (and do what the hated Blair was unable to do).

This morning they had in the Commissioner of the Metropolitan Police to back the Government and disparage the Director of Public Prosecutions.

This afternoon, we had the Director of Public Prosecutions himself. He, sensationally, had come out against the proposal to extend the period, and we all wanted to see whether he'd been got at.

First, sniping. The Government controls the cast list at these sessions. Labour wanted Sir Ian Blair (one of their few friends in the matter). The Opposition wanted Stella Rimington to be called as well (one of many opponents). The former was invited; the latter rejected. This selection process needs changing.

And our old friend John Bercow chairing the meeting made a mistake by devoting the first two thirds of the session to minor matters and running out of time for the interesting stuff. Not Speakerly.

Having said that, what did we have? It depends what you make of Ken Macdonald as a person. What can we tell about someone from a 50-minute appearance in front of a committee?

The best that can be said, and there is no higher compliment, is that he betrayed no sense, no hint of politics. There was his voice (calm, decent, gentle even), and then what he used it to say.

Sir Ian had claimed it was "inconceivable" that intercepts could be implemented for years. "That sounds a little pessimistic to me," Sir Ken said. And what about the other assertion, that prosecutors were only involved at a late stage of the case and were therefore unaware of the complexities. "Is that a characterisation you'd share?" David Heath asked.

"Not at all," Sir Ken said as crisply as you can if you have that voice and manner of his. He went on to rehearse the 93 per cent success rate in terror prosecutions, the intimate collaboration with the police as the cases developed, the involvement beginning even when operations were being designed.

But he wouldn't let himself be drawn into conflating 42 days with internment, or suggesting that it would contravene Article 5 of the Human Rights Act, or to say that 42 days would never be needed – "the question is whether it's remotely likely". He had no moral objection to it, no view on its effect on intelligence, but in precise reply to a question, he revealed had not been got at. "Professionally, I say we see no need to extend it."

Politically it's a different matter, as it usually is.

simoncarr@sketch.sc