Leading article: A table for two at No 10

Our preference was for a coalition based on Labour and the Liberal Democrats, but we accept that the parliamentary arithmetic was against it. Given that we said that electoral reform was the big prize, and that the Liberal-Conservative government promises a referendum on it, this newspaper is happy to give the new administration a fair wind. The policy agenda of the new government is a compromise, from which some good things flow. The cancellation of Labour's third runway at Heathrow is an important step in the green direction supported by The Independent on Sunday. Other environmental issues are more difficult, which is why we have devoted this special edition to an analysis of whether blue and yellow really do make green.

Other elements of the common programme agreed between the parties are welcome: scrapping ID cards and the national child database; opening up the schools system to new providers; banking reform. Our doubts concern the timing of public spending cuts, on which Vince Cable seems to have capitulated in accepting them this year, and Europe, where we cannot believe that the Conservative Party's self-imposed exile to the Czecho-Polish fringe is in the national interest. But that is part of the give and take of co-operative politics. The one part of the coalition agreement that really does not fit into this rosy view is the proposal for a 55 per cent threshold for a Commons vote to seek a dissolution and an election. (David Cameron has now hinted that this, too, might be subject to compromise before becoming law.)

As much as the policies themselves, we welcome the process by which the common programme was negotiated. For too long, politics and the reporting thereof has been dominated by metaphors of conflict in which the winner takes all. One of the refreshing aspects of the new government is that formerly tribal politicians such as David Cameron, George Osborne and William Hague have suddenly discovered the virtues of compromise and collaboration.

So enthusiastic was Mr Cameron at his joint news conference with Nick Clegg in the garden of No 10 about the joys of parties working together that it invited the question: What, then, is so wrong with PR? A truly proportional voting system would require parties to work together most of the time.

Not that the choice to be offered in the referendum is a proportional system. The alternative vote is likely in practice to be only slightly more proportional than the existing system. The Electoral Reform Society estimates that the Lib Dems would have won 22 more seats under AV than they did on 6 May, most at the expense of the Conservatives. But it is a better system. It would allow voters to express their genuine first preference while also influencing the choice between whichever two candidates emerge as most popular in their constituency. And it would preserve the link between an MP and a single constituency, the main strength of first past the post.

Ultimately, this newspaper might prefer AV plus, as advocated by Roy Jenkins in the dawn of the age of Blair. The Jenkins report proposed, in addition to the alternative vote in single-member constituencies, the election of 20 per cent of added MPs in groups of constituencies, designed to "top up" party representation to match share of the vote more closely. This is not a practical option as yet, but the alternative vote is. As we report today, the referendum on it is eminently winnable. Our ComRes poll suggests it could be carried by a two-to-one margin – although there is first a campaign to be fought. We offer an exclusive preview to that today.

A more co-operative politics should not mean fudge and mudge. It is one of the weaknesses of the coalition that the Prime Minister and his deputy should look and sound so similar. That may have implications for the Labour leadership contest. David Miliband, the early front-runner, is undoubtedly very able. But, despite a comprehensive school education, he does seem to come from the same production line of professional politicians that produced the leaders of the new government. It would be healthy if Yvette Cooper, the former work and pensions secretary, could be persuaded to give the Labour selectorate a wider choice. But that is a story that should be allowed time and space to develop.

Meanwhile, with a green verdict pending, but above all for the prospect of a permanent change to a fairer voting system, the Cameron-Clegg government deserves a cautious welcome.