Welcome to the Sovereignty Queue, another benefit brought to you by Brexit!

EDIT: Lots of people seem confused by this:

Prior to Brexit, because the EU was not in the Schengen area, you needed to show a passport to enter the EU, but it was an EU passport so that was simply a scan. In busy airports, you could use the ePassport gates. Now, you must have the passport stamped with the entry date, because you cannot spend more than a certain amount of time (three months?) in the EU, in total, in one year without a visa.

You must also have the corresponding exit stamp. This was not previously necessary for people taking Schengen to UK flights: you would have your passport checked at the UK border (a handful of places did this at the non-UK end) for UK entry. For non-EU passports, I believe the UK also handled the leaving-Schengen bit for these legs.

The additional steps where they have to check how long you've been in the EU, stamp the passport, and (now) check biometrics adds time in both directions. It means you now need to see a human where previously an electronic entry thing was necessary. No EU country is incentivised to put more people on these desks, because why would you reward a country for doing stupid things? It just encourages them to do more stupid things. And so British people all get annoying delays travelling. Oh, and to actually have a functioning economy, we have to comply with all EU regulations (because they're most of our export market), but now we don't get a say in drafting those laws (which actually is a benefit of Brexit, because the most monumentally stupid EU laws were pushed by the UK on behalf of the USA). All this in the name of sovereignty and controlling our borders.

In Alastair Reynolds' Demarchy, anyone who voted for Brexit would have their future votes' weights scaled back to 0.5.