In the pretty central square of Plzen (Pilsen), the Czech town famous for its lager, the Civic Democrats are doing their best to pull in a crowd.
As the politicians wait under vast blue umbrellas, party workers hand out blue and white balloons and blue candy floss to the crowd. The kids are captivated and the occasional mum or dad is persuaded to take a leaflet on the European elections.
This party, known here by its initials ODS, until very recently was the Czech government. And they're Mr Cameron's new best chums.
After the Euro elections in the first week of June he wants to form a new group in the European Parliament, breaking away from the Christian Democrat, pro-European integration, European People's Party. He'll need MEPs from six other countries to do it. The Civic Democrats and the Polish Law and Justice party will be the mainstay.
I hoped to be at the launch of the Tory Euro campaign today, but no doubt it will be dominated by questions of moats and mortgages, so I thought I would have a look at their main new allies.
There is more temptation for the crowd, who are being wooed by two musicians in folk costume playing a lively tune - one on an instrument that looks a bit like a bagpipe, if a bagpipe was in the shape of a sheep being sick into a golden horn.
But what is the temptation for the Civic Democrats, I ask the leader of the party's group of Euro MPs. Jan Zahradil tells me that it is bad for democracy that the European Parliament is dominated by two big groups of the left and right and that there is no real opposition. He wants a group that will be in favour of a looser relationship within the EU, less red tape and more reform of the Common Agricultural Policy.
But is the vision really the same?
It has been a torrid time for the Civic Democrats. They were ejected from government after losing a confidence vote because of the rebellion of two of their MPs, who were angry their party had signed and ratified the Lisbon Treaty. The current President Vaclav Klaus resigned from the party he founded over Lisbon. And now the Civic Democrats want to join up with a party whose main European policy is... opposition to Lisbon.
I asked the former prime minister and party leader, Mirek Topolanek, what he really thought of the treaty he had backed at such a cost.
"This treaty is bad and we know it. We supported the treaty among other things because we were a party in government and because we signed it and because we agreed on a compromise at the level of the European Council.
"I have to point out that we're a much smaller country than Great Britain, and we only have a chance of promoting our national interests as part of a larger collective such as the European Union. We have no alternative.
"If we hadn't signed the Lisbon Treaty and had been pushed to the sidelines of the European Union we would have had no chance of promoting our national interests. That's the main reason. It was the lesser of two evils."
"Do you want it to fail? Do you want Ireland to vote 'No', Britain to vote 'No'?" I asked.
"It's a purely British matter, and I would not dare to get involved in it. I signed the treaty, and I put through ratification. The Czech Republic is simply a different country from Britain. If Britain had lived with communism for 40 years than they'd have less of a problem with the Lisbon Treaty."
I persisted: "But you're linking up with a party that says it wants it to fail, that says it's a bad thing".
"That doesn't really bother me."
"But you disagree on something fundamental."
"I don't think so. And once again I'll try and explain it in a positive way. Our co-operation is NOT based on what we DISAGREE on. Our co-operation is based on something that we want to build together. And what we want to build together has nothing to do with the Lisbon Treaty."
They are hardly on the same page on one of Mr Cameron's main international policies either. The Civic Democrats' old leader, the president, says climate change is a myth. Mr Topolanek is more circumspect.
"The Civic Democrats want people to live in a healthy natural environment. I don't think it's that different from the sort of policies that David Cameron is pushing for, the only difference is that we're not so intoxicated with the mantra of climate change."
Mr Cameron can live with that, although his opponents will make hay. His real aim is to avoid any linkage with homophobes, racists or others on the extremes, to say of the new group: "no nuts were used in the making of this product".
The Civic Democrats are not weird, if you exclude the sheep-shaped bagpipes. But their vision of the EU may turn out to be very different from that of many Conservatives.