Andrew Grice: Ed sets the pace with his focus on responsibility

As his aides downed Peroni beers left over from a party for Labour MPs, Ed Miliband was stone cold sober as he suddenly cut through the legal knots his advisers had tied themselves up in.

It was 10pm on Monday as Team Miliband struggled to finalise the wording of a Commons motion on News Corporation's bid for full control of BSkyB. Ten drafts came and went, some trying to delay the Competition Commission's decision on the bid by linking it to the police investigation into hacking. Then Mr Miliband had his flash of inspiration, saying: "This House believes that it is in the public interest for Rupert Murdoch and News Corporation to withdraw their bid for BSkyB."

Simple and effective. The Conservatives might have opposed a motion about the Commission's inquiry, possibly aided by Liberal Democrat ministers. If the Commons spoke with one voice, even Mr Murdoch would find it hard to resist, Mr Miliband said. He was right. Before Wednesday's debate started, News Corp had pulled its bid.

Mr Cameron, who rang rings round Gordon Brown over MPs' expenses, has been running to catch up with Mr Miliband on the hacking issue. The Labour leader has shown better judgement, being the first to call for a public inquiry and for yesterday's resignation of Rebekah Brooks.

When Mr Miliband called a council of war on Thursday, his advisers focused on how to build on this unexpected platform and tell the voters something big about Labour's direction. Five weeks ago, Mr Miliband made a speech about the need for "responsibility" at both the top and the bottom of society. This was the real Ed, a product of his deep thinking about the challenges facing the country.

It wasn't about the media, more about fat cats and welfare claimants. But on Thursday his team concluded it was highly relevant to the hacking affair because "power without responsibility" has now been exercised by the press and the police, following the banks and MPs (over their expenses).

So perhaps the time has come for Mr Miliband's responsibility agenda. We will certainly be hearing more about it. This road, while attractive, also has potholes. For a start, do the institutions Labour will "take on" include the trade unions? They threaten both an autumn of strikes and a block on some of Mr Miliband's plans to dilute their influence in his party. There be may limits to his boldness.

MPs wonder whether hacking will prove a game-changer for British politics, as some Labour folk dare to dream, or whether normal service will resume shortly. "The next election won't be fought on media regulation," one Miliband aide admitted yesterday. "This is only the start." Yet it might just be the start of something big.