AOG.
What actually happened was Cameron made a U-Turn which wrong footed Brown, but Tory U-Turns don't sell the Daily Mail.
In May 2007 the Commons voted on on a bill to exempt themselves introduced by former Tory chief whip David Maclean. Both the Tories and Labour had a free vote. Cameron astained but many Tories voted in favour of it.
This was tested in 2008 when the High Court ordered MPs had to reveal their expenses. MPs didn't want to reveal them so a new Order was drafted which would have given them immunity. Tory and Labour were both conniving to suppress this information.
Then on Monday, Alan Duncan became the new shadow leader of the house in the Tory reshuffle, and persauded Cameron to put on a whip to vote against exemption rather than a free vote.
Cameron's U-Turn thankfully killed off this pernicious bit off proposed legislation.
When the Government received this information, they conceded defeat.
http://blogs.telegraph.co.uk/iain_martin/blog/ 2009/01/22/david_cameron_at_war_with_his_old_g uard_over_mps_expenses