THE French cockerel and the German eagle have strutted together for so long that few took much notice of this week's 50th anniversary of the Elysée treaty that sealed their partnership in 1963. The pairing has known memorable times: think of de Gaulle and Adenauer, Giscard d'Estaing and Schmidt, or Mitterrand and Kohl holding hands at the site of Verdun. Now Angela Merkel and François Hollande must tend the near-sacred relationship, a pillar of peace in Europe and of wider co-operation in the European Union. On January 22nd they went through the pomp of celebration in Berlin with joint cabinet meetings, speeches to assembled German and French parliamentarians and an encounter with young people from both sides of the Rhine. Yet for all the words of undying friendship there was something tired and loveless about it all. French opposition leaders talk of relations being marked by "indifference" and even becoming an "empty shell." Perhaps this is because Mrs Merkel and Mr Hollande come from rival political families. Perhaps they don't yet know each other well (though in public they use the familiar tu and du forms, in private they can converse only in English). Or maybe it is because Mr Hollande, unlike Nicolas Sarkozy, does not try to disguise his differences with Mrs Merkel. Still, the two leaders are trying to preserve the flame. They promised unspecified plans in June to deepen euro-zone integration. And they listed dozens of new initiatives, from promoting youth exchanges to a co-ordinated energy policy. Yet the range and vagueness of the proposals suggest a lack of substance. Mr Hollande has forgotten his campaign promise to present an updated Elysée treaty. All this reflects a deeper malaise. France and Germany have stopped dreaming of a joint destiny. The ambiguity of the EU's "ever closer union" is under strain. The euro is a troubled child: a single currency without a single state that is questioned by markets. But like many couples that have cohabited for a long time, France and Germany hesitate to pledge permanent union. Crudely put, Mr Hollande thinks the problem could be solved if only Germany would commit more money, through Eurobonds, say. Mrs Merkel says the main issue is financial discipline; she sees joint liability as impossible without political union. Both leaders bear scars. Mrs Merkel knows that many Germans feel cheated. They gave up the D-mark on the promise that they would not have to pay for others - only to be forced to bail out the likes of Greece after all. For his part, Mr Hollande does not want to reopen the splits in his Socialist Party over the failed referendum to approve the EU's constitutional treaty in 2005. So the patriarch and matriarch find it easier to avoid talking of the future at all, preferring to muddle along. Maybe their determination to avoid breakdown is an achievement in itself. The euro zone seems to be stabilising. Mrs Merkel and Mr Hollande gave the nod for the European Central Bank to threaten intervention in the markets. They have started to build a banking union. And they have stopped Greece falling out of the euro. Inevitably, the Franco-German partnership is bound up with relations with others, notably Britain. The Elysée treaty was signed days after de Gaulle had contemptuously vetoed Britain's bid to join the European project, an exclusion that lasted a decade and stirred British resentment. The German parliament ratified it only with a preamble advocating British membership and restating Germany's commitment to NATO. The general said "treaties are like roses and young girls. They last while they last. Even as France and Germany agonise about their future, Britain is rethinking its relations with them. Just a day after Mrs Merkel and Mr Hollande cheered Europe's ever closer union, the British prime minister, David Cameron, set out his vision of an ever looser relationship. At one point the hapless Mr Cameron had even planned to deliver his speech in Germany on the same day as the treaty commemoration. His call for renegotiation, followed by a British referendum, provides France and Germany with more reason to avoid a new treaty. Although the two leaders may give Mr Cameron something, he could be overestimating his bargaining position: a joint article by their foreign ministers declared that an "à la carte Europe" is out of the question. Vive la différence For all its problems, the relationship between France and Germany remains remarkable, not just because it overcame war bitterness but also because it transcends deep political differences. On economic and trade policy the Germans are closer to the liberal British than to the statist French. On geopolitics the French share Britain's interventionism, in contrast with Germany's pacifism. Take the unilateral French military action in Mali: the French are grateful to Britain for prompt logistical support and irritated by German squeamishness. The true importance of the Elysée treaty lies not so much in reconciliation (that began much earlier) but in how it made tight co-operation across the Rhine routine at all levels of government. France, once the dominant partner, is now weaker. Germany has reunited, and the EU's enlargement to the east gives Germany new "essential" partners, particularly Poland. The euro crisis has thrust Germany reluctantly into a leadership role and cast a harsh light on France's reluctance to reform. Mr Hollande has tried to court Spain and Italy; Mrs Merkel has at times linked arms with the Netherlands and Finland. But in the end France and Germany still need each other, just as the EU needs them. As the biggest economies, each can block agreement. When the two manage to reach a compromise despite starting from such different world views, few others will oppose the result. The coq and the Adler are destined to stick together.