David Cameron has made a sparkling début as Leader of the Opposition. By his actions in his first few days he vindicated the Conservative Party's choice of him, by a margin of two to one, over David Davis. Of course, it is possible to place too much emphasis on how well he performed in the House of Commons - the skills tested are essentially theatrical and superficial. Yet command of the House and the ability to engage effectively in debate do matter. Mr Cameron promises to raise the level of that debate by agreeing with the Government when it is sensible to do so, while also offering the prospect of holding Tony Blair to account more frequently than any of his four predecessors.

Mr Cameron has made a good start in his choice of early priorities. After an election fought on a narrow-minded and backward-looking platform of immigration and crime, his decision to make education and the environment his first two subjects is refreshing. We welcome the emphasis on both, not least because it will keep the Labour government on the mark. On schools, the Government's plans may be flawed, but the greater danger comes from small-c conservatives on the Labour back benches than from misplaced radicalism on the front bench. As Mr Cameron said, with his support, the Prime Minister "can afford to be as bold as he wants to be".

And on the environment, Mr Cameron shows an impressive understanding, and a degree of personal commitment unusual in mainstream political leaders. His strategy, born both of interest and a shrewd eye for a winning issue that will change his party's image, promises a long-overdue greening of British politics.

The new Tory leader will have an impact beyond the polite clash with Mr Blair that will continue to dominate British politics for some time yet. First, the Liberal Democrats must ask themselves some hard questions about their hold on the crowded centre ground, and Charles Kennedy must make from scratch his case to lead the party into the next election. Second, the advent of Mr Cameron has got Gordon Brown bothered. As the likely next prime minister, the Chancellor is under pressure to raise his game, not just on green issues but on the effectiveness of his programmes for tackling poverty.

For the sake of the environment, of social justice and of the quality of our democracy itself, we welcome Mr Cameron's arrival.