By Ray Furlong
BBC Radio 4's The World At One
Germany's Christian Democrat CDU party, triumphant in the country's recent general election, has downgraded relations with the Conservatives.
The change follows David Cameron's decision to remove his party's MEPs from the centre-right European People's Party (EPP) group in the European Parliament.
Ties have loosened between David Cameron and Peter Altmaier's CDU
Joint policy groups have been scrapped and an annual meeting has been cancelled.
The changes have left critics of the EPP move to claim their prediction - that the Tories would lose influence in Europe - has been fulfilled.
"The fact that the Conservatives have decided to leave our family of course has some institutional aspects that cannot be neglected," said the senior CDU MP, Peter Altmaier.
Mr Altmaier was co-chairman of one of three joint working groups, set up with some fanfare by David Cameron and German Chancellor Angela Merkel in 2007 to discuss policies.
He added: "When you're no longer a sister party you have a different type of relationship. This is something that has automatic consequences.
"The relationship to EPP sister parties is more intense."
David Cameron pledged to cut the Conservatives' ties with the centre-right grouping during his 2005 Conservative leadership campaign.
A new group, the European Conservatives and Reformists, which includes 55 MEPs from across eight member states, was formed after June's elections to the European Parliament.
The Tory leader has forged links with ex-Czech PM Mirek Topolanek
Mr Altmaier acknowledged that the working groups had concluded their work, but added that when the time came to form new ones the CDU would be looking to their partners in the EPP.
A senior German source who was closely involved in establishing the working groups was more candid: "We knew the Tories would pull out of the EPP in 2009, so we saw no reason to continue with the groups."
He added that, for the same reason, no Tory MPs had been invited to come to Germany as observers during the recent election campaign, as they usually would have been.
"We actually have more in common than ever before, but it's overshadowed by the European situation," the source said.
No go Como
Another example of the changing bilateral relationship is the annual gathering on the shores of Lake Como in Italy.
These have been taking place at the former summer residence of Germany's first post-war leader, Konrad Adenauer, since 1985.
This year it was cancelled - another victim of the split.
The Tory grandee and former European Commissioner Lord Brittan believes the importance of such gatherings should not be underestimated.
He said: "They are important, because how do you get influence in the European Union? You do it by building up alliances, by talking to people and you don't do it overnight.
"You can't just turn up at a meeting and say: 'This is what I want'. Whether you are likely to get it depends on the kind of relationship you have built over a long period of time.
"So if the number of links are reduced and there's a feeling of ill-will, that gives you a mountain to surmount."
A hostile act?
Britain's former ambassador to Berlin, Sir Peter Torry, believes the Cameron-Merkel personal relationship has been rocky ever since he won the leadership of the party. They disagree fundamentally over the EU's Lisbon Treaty, which Mr Cameron wants to put to a referendum.
"The Germans wouldn't see him," he said.
The damage is there... but there are important areas where we need the Germans
Sir Peter Torry
Former UK ambassador to Germany
"They saw the decision (to leave the EPP) as contrary to their interests and they made their displeasure clear by not meeting him for quite some considerable period of time."
In fact, Mr Cameron only finally met Mrs Merkel in September 2007, two years after he was elected Tory leader.
"Certainly the damage is there," added Sir Peter.
"Mrs Merkel and her team view this as something of a hostile act.
"I think if you look ahead a lot will depend on Lisbon, but leaving that aside there are important areas where we need the Germans: reform of the EU budget, forming a sensible EU energy policy, Afghanistan
and tension at the top makes it that much more difficult to achieve all these objectives."
Nevertheless, the Conservative leadership has always insisted good relations can be maintained and that outside the EPP they are "happier neighbours rather than unhappy tenants" of their political allies.
The Tory MP Steven Dorrell, a member of the all-party British-German parliamentary group, agrees and argues that the spat over the EPP is "ephemeral".
"The CDU do have a desire to re-activate relations," he said.
"In opposition we're a junior partner. But once in government, we're natural allies."
Others, including those on the pro-European wing of the party such as Lord Brittan, agree that the realities of being in government could improve the relationship.
"I am told that the leadership is trying to repair the damage and stressing their wish to have closer links with the CDU.
"But they've got to work that much harder."