Despite David Cameron's recent charm offensive in Berlin, where he spoke about his hope for EU reforms ahead of the EU referendum on membership, senior German figures are uneasy about the British "renegotiation" that is about to begin.
They fear Britain's toxic domestic debate on Europe may drive Mr Cameron towards counterproductive tactics, including the tabling of impossible demands.
The blunt, win-or-lose negotiating style that prevails in Westminster does not necessarily work in the consensus-seeking EU, and the Germans feel it might lose the PM potential allies.
Another worry is that many Britons assume the renegotiation will be mainly a bilateral conversation with Germany, whereas 26 other countries will come to the table with their own views too, as well as the European parliament and commission.
They also ask whether Mr Cameron may put party unity ahead of winning the referendum: a few days ago, after he had said that Conservative ministers would have to back him in the campaign, he changed his mind under pressure from backbenchers.
The biggest concern in Berlin, however, is that many of Britain's demands may be impossible to satisfy. Take Mr Cameron's priority of limiting EU migrants' rights to in-work benefits such as tax credits. The EU treaties ban discrimination over conditions of work -- which include in-work benefits -- on grounds of nationality. The Germans regard that principle as fundamental to the EU and know that the Poles and many others would never agree to scrap it. (The UK could, however, more easily restrict access to unemployment benefits.)
Another British priority is "safeguards" for the single market, against the risk of the euro countries caucusing and then imposing their wishes on the wider EU. Financial regulation is a particular concern, given its impact on the City of London. But German officials point out that the Eurozone governments never have caucused and will not countenance a veto for the City on financial rules -- which they would view as an unfair privilege for one member.
A third demand is for national parliaments to play a bigger role in curbing unwarranted EU laws. The treaties say that if a third of the parliaments raise a "yellow card" against a draft law from the commission, it must withdraw or justify the measure. But although several governments share London's desire to strengthen this procedure, Germany does not as it fear it could slow down or stymie the passage of essential laws.
London and Berlin agree that the EU should be more competitive -- forging trade deals with other parts of the world, cutting back red tape and extending the single market. But the new European Commission is already doing these things.
They may also be able to agree on the methods for delivering reform. Mr Cameron says there needs to be "treaty change". A proper revision, involving ratification by all 28 member states, could not be completed before his referendum. But Angela Merkel is open to the possibility of a document promising treaty change at some point in the future. The Danes were given a set of promises in 1992, after voting against the Maastricht treaty. However, a list of promises to the UK would need the approval of every member state, so could not touch on sensitive topics such as freedom of movement.
The Germans' desire to keep Britain in -- not only for its economic liberalism, but also to prevent Germany's own power becoming too preponderant -- makes them keen to help Mr Cameron. But senior German figures warn this will not be at the price of abandoning the EU's core principles.