When the Culture Committee last questioned News International executives about phone hacking, it raised almost as many questions as it answered. Today's milestone hearing gives MPs another opportunity to pin down some much-needed facts. It is an occasion to which they must rise.

Much has changed since Rupert Murdoch, his son James, and former NI chief executive Rebekah Brooks appeared before the committee in mid-July. Harbottle & Lewis, released from a confidentiality clause, says its inquiries into NI were of narrow scope and limited conclusion, and the Murdochs' use of them to bolster their "rogue reporter" defence was "inaccurate and misleading".

Then there were the multiple queries over James Murdoch's testimony, not least his statement that he had not seen the incriminating "For Neville" email when he signed off a £1m out-of-court settlement to Gordon Taylor.

Today's witnesses – including Tom Crone, a former NI lawyer, and Colin Myler, a former editor – should be able to shed significant light on these matters. But it will take persistent and well-informed questioning to get to the bottom of the contradictions raised so far.

Previous hearings have been weakened by allocating all members an equal number of questions when time would more profitably be given to experts such as Tom Watson. Today could see significant progress in getting to the truth about hacking. But the Culture Committee will need to raise its game.