I'm reading The Fire Engine That Disappeared, a Swedish murder mystery by Sjowall & Wahloo, and I came across this passage:
That the Swedes and Danes understand each other's languages with the minimum of effort is a truth which over the years has been carefully cherished at high levels in both countries. But this is often a truth with provisos, and even more often something more serious, a case of wishful thinking, for instance, or an illusion. Or to put it bluntly, a lie.
Two of the many victims of this wishful thinking were Hammar and a prominent Danish criminologist, who had known each other for many years and often met up at police conferences. They were good friends and each used to make highfalutin statements on how they had each mastered the other's language with the greatest of ease, which any other normal Scandinavian ought to be able to do, a sarcastic addendum they seldom neglected to make.
This was so until, after a decade of hobnobbing at conferences and other high-level meetings, they met for a weekend at Hammar's country cottage, when it turned out that they could not even communicate with each other on the simplest every day matters. When the Dane asked to borrow a map, Hammar went and fetched a photograph of himself, and then it was all over. Part of their universe had collapsed and after celebrating formal orgies of foolish misunderstandings for a few hours, they went over to speaking English and discovered that they did not really like each other at all.