The answer lies in the enhanced capacity for the EU to act on the world stage. At present, the representation of the EU to third countries is divided three ways between the High Representative for the CFSP, the European Commissioner for External Relations and Neighbourhood Policy, and the foreign affairs minister of the member state that holds rotating presidency. Not surprisingly, this can sometimes be confusing.

The new treaty contains a modest but significant reform: to bring together the roles of Council representative and Commissioner, and to install that person as permanent chair of the foreign affairs council. This reshuffling of the roles could have a big practical effect. There will be a consistent voice for the European Union – Henry Kissinger's famous request for a phone number to call will now have an answer. Clarity will replace complication, and disruption will give way to continuity.

Europe will get a louder voice in the world, which Europe needs, and which the world needs.

It was envisaged in the constitutional treaty that this new merged role would be called the "Foreign Minister." This was a misnomer, and has rightly been dropped, for the EU representative will not be a foreign minister as conventionally understood.

In a national government, the foreign minister is both the chief representative on matters of foreign policy and also the main decision-maker. He or she can take decisions that matter and give undertakings that will stick. The EU's representative will not have quite the same powers.

Decision-making will remain in the hands of the foreign affairs council, where all 27 member states are represented. That council will continue to vote, as now, by unanimity on policies, turning to QMV for implementation. The vast bulk of the assets used in foreign policy – diplomatic representation around the world, contacts and relationships, and above all military power – remains in the hands of the member states, and will not be at the command of the EU.

It is clear that this reform does not mean more powers for Brussels. Instead, it means that Brussels will be able to use better the powers it already has. This is reason for celebration, and not for a referendum.

There will be many people who regret that the treaty does not go further in strengthening the foreign policy of the European Union, enabling the use of QMV in making policies as well as implementing them, but even they will agree that the improvements it does contain are still a useful step forward.

Of course, the real test of foreign policy will come in practice and not in theory. The world is changing fast, and the different European countries need to work together if they are advance their interests and defend their values. The rise of China, the chaos in Gaza, and the fight against climate change are all issues where Europe has a common interest but not yet a common voice.

The new treaty will give them that voice. This is the right reform, taking place at the right time.

But it is one thing to have a common voice; it is another thing to use it. Having reached agreement at the summit, this is the next challenge for Europe's leaders. But in the meantime, they have given themselves a good start.

The author is director of Federal Union