THE PACE of geopolitical change seems more hectic by the week. For Britain, one effect ought to be a new emphasis on stronger links with the European Union. A planned UK-EU summit in London on May 19th is an important chance to start improving post-Brexit relations. Vladimir Putin’s war in Ukraine and, especially, Donald Trump’s recent antics on tariffs and his startling revisionism on Russia have injected new urgency into Europe’s need to bolster its own security. That is likely eventually to bring Britain and the EU closer together—but there are some obstacles along the way.