Key questions over expenses report

Sir Thomas is a former Whitehall mandarin who served as an external member of the Commons Audit Committee from 2004 to last year – so is very familiar with the expenses system that was in place.

After the row erupted when details of MPs' claims were leaked in May, Gordon Brown and the Parliamentary authorities recruited Sir Thomas to re-examine how public money had been spent.

Why has the process proved so controversial?

When the ruling Commons Members Estimate Committee first authorised the independent audit in June, it agreed claims from 2004/8 would be assessed "against the rules as they existed at the time".

So MPs receiving letters from Sir Thomas in October were annoyed to find he had retrospectively introduced "reasonable" levels of spending on items such as gardening and cleaning. As a result, hundreds are thought to have been asked to return cash.

Did they pay up?

A large number had already handed back money after coming under fire from the revelations in May. All the main party leaders urged their MPs to comply with the review findings in the interests of restoring public trust.

But some backbenchers suggested they were willing to fight the demands in court. Partly to placate this anger, the House authorities set up an appeal process and installed former senior judge Sir Paul Kennedy as the final arbiter of who should repay what. In total, 80 MPs – around one in eight – launched appeals.

What do we know about Sir Paul's view of the cases he considered?

Sir Paul notified the MPs of his decision last week and many have already made the results public. A large proportion either had their repayments reduced or overturned, as the judge appeared to disagree with Sir Thomas's use of retrospective limits.

MPs who did not appeal may now feel they could have cut their bills significantly. There may be some pressure for the appeals process to be reopened.