I was tipped off yesterday evening that an emergency meeting of the Cabinet had been called for eight o’clock this morning. Members hadn’t been told the reason for the summons, which itself was extremely unusual – and couldn’t find it in the media, either, which is also unusual (since Ministers are more likely to find out important government plans for other departments by reading the papers than from Downing Street itself).

As it happens, one paper was briefed about the meeting – the Sun, which reported yesterday evening that “a new law will be rushed through Parliament” to give the security services and police access to phone and net records. In the balance of the argument between security and liberty, the Sun leans emphatically towards the former, unlike the Mail and Telegraph stables. It also says that “emergency new powers will be unveiled today to allow enshackled MI5 and cops to probe the internet for terror plots again”.

However, the Guardian suggests this morning that surveillance powers are to be restricted rather than extended – because Nick Clegg has struck a deal with David Cameron and Theresa May over the Regulation of Investigatory Powers Act. Either way, it’s clear that Downing Street is moving very quickly and that advance briefing has been confined. Legislation is reportedly to be rushed through Parliament within a week. Any sceptical Cabinet members might feel that they are being bounced.

The Labour leadership apparently accepts the case for the new legislation: namely, that it will require internet and phone companies to retain personal communications data for 12 months and allow the security services and police to access it. Ministers understood the law already to allow this arrangement, but it is being challenged in the courts in the wake of a recent European Court of Justice ruling – hence the dash to Parliament.

None the less, the devil will be in the detail (as ever). One man’s security measures are another’s snooper’s charter, and civil liberties groups are already claiming that the review is cover for a backdoor revival of the Data Communications Bill. The details of the revision may not yet have been settled, but the choice in principle is clear – namely, the trade-off between widespread surveillance and targeted measures.

In opposition, the Party argued for the latter, pressing for intercept evidence to made available in court, which was also the Liberal Democrats’ position. In Government, both parties have gone along with objections to the move – such as worries about the costs, doubts about legality and warnings that security service techniques would be exposed during legal proceedings (though other Anglosphere countries have found a way through these thickets).

The easiest course for the security services and police to take is to argue for a simple extension of surveillance powers. This may be understandable, but it should be resisted. Very simply, human intelligence is more likely to turn up evidence of terror plots than mass trawls. There will always be voices to claim that the latest security threat – yesterday, Al Qaeda; today, ISIS; tomorrow, another Islamist terror group (in all likelihood) – justifies sweeping surveillance measures. But the best means of preventing future 7/7s and protecting other Lee Rigbys is intelligence.

As it happens, the perpetrators of both atrocities were on the security services’s radar. The latter argue that they need more resources to keep us safe – and the threat is real and their work invaluable. The clear and present danger to our national security is from violent Islamism. The case for shifting defence resources from external to internal security is thus as strong as ever. We need more spies and informers – not to put too fine a point on it,