On the second page of the Death Guard Codex background section there is a Brexit joke. You see, it turns out that before they were reunited with their Primarch the original Death Guard, the Dusk Raiders, “were drawn from the rugged gene-stock of Albia, a Terran empire that long resisted reunification.”.
So the Death Guard, an army of chronically depressed unimaginative footsloggers who worship decay and despair, are British and even twenty-eight thousand years in the future the British people are stubbornly resistant to political unification with the rest of the world. Even when the cause of unification is led by a literal god trying to drag the human race out of an apocalyptic dark age we're still desperately protecting the pound.
I love it. Not only because I'm one of those tiresome Remoaner people but because its nice to see 40k getting some of its grim(dark) humour back. One of the biggest spiritual ancestors of the Imperium is Judge Dredd, another property that a lot of people tend to forget is meant to be funny.
As I've said before, one of my minor favourite background details of 40k is that Nurgle Daemons like fighting alongside Noise Marines because they like dancing to the screeching discordant sounds.