Things are getting interesting in Europe.

Boris Johnson has transformed the terms of the EU referendum debate by announcing that “after a huge amount of heartache” he is to throw his weight behind the campaign to take Britain out of the EU.

The London mayor announced on Sunday that he will campaign for a leave vote after concluding that David Cameron’s deal will not deliver the reformed EU he promised.

Speaking outside his home in north London, the mayor said his decision had been “agonisingly difficult”. But he added: “I would like to see a new relationship based more on trade, on cooperation, with much less of this supranational element. So that is where I’m coming from and that is why I have decided, after a huge amount of heartache, because the last thing I wanted was to go againstDavid Cameron or the government, I don’t think there is anything else I can do.

“I will be advocating Vote Leave – or whatever the team is called, I understand there are a lot of them – because I want a better deal for the people of this country, to save them money and to take control. That is really what this is all about.”

Downing Street issued a low-key response. A No 10 spokesman said: “Our message to everyone is we want Britain to have the best of both worlds: all the advantages of the jobs and investment that come with being in the EU, without the downsides of being in the euro and open borders.”

Essentially, many in Britain think that their nation’s membership in the European Union costs more than it’s worth. The increasing regulatory regime of the EU is threatening the British economy. What’s aggravating the issue is the migrant crisis in mainland Europe where their lenient migrant policies are creating huge costs and problems for which the EU wants nations like Britain to pay.

Remember that it was only in 2014 that there was a huge national debate in Britain about Scotland cleaving from Britain and becoming an independent nation again. A big part of that debate centered around Scots’ desire to join the EU as an independent nation and reap the perceived benefits that smaller, poorer nations enjoy with their EU membership. In that vote, the Scots agreed to stay part of Britain, but it wasn’t a landslide (55% to 45%). Now all of those same Scots will vote on EU membership.

Britain won’t vote until June 23rd. It’s going to be a long, passionate debate.