BRUSSELS — A bereavement. A horrific accident. An emotional spasm. For once, the language coming from the glass and concrete buildings in Brussels is laden not with the dull acronyms of European Union jargon, but with angst.

For many of the Britons who spent years, even decades, working to integrate their nation within Europe, June’s referendum vote to quit the bloc was traumatic.

Like battlefield survivors, marooned on what feels increasingly like enemy territory, they are coming to terms with a new reality: As British influence recedes here, so, too, do their careers.

They tell tales of colleagues going for coffee when they speak at meetings, or being cut out of email chains. One official said he was treated like a bereaved family member — people avoid you, he said, because they don’t know what to say.