I'm planning to go to London in November with my partner, but I'm not sure if I need to apply for a visa or if they'll let me in with just my passport. I've read conflicting things online and I don't want to show up at the airport and run into problems.
As a Spanish citizen, you only need a valid passport to enter the UK as a tourist - no visa required. What I do recommend is checking ETIAS before you travel (it's a new requirement they wanted to implement, so check the official UK government website to see if it's already active by the time you travel in November). Bring your passport in good condition, and if they ask, you'll need to show that you have funds for your stay and a confirmed return flight, but that's the standard stuff they ask for everywhere.
I've traveled to London several times without a visa, just with a valid Spanish passport, so that's clear. What the other answer mentions about ETIAS is important: it's an online procedure you'll need to do before you leave, it costs a few euros and doesn't take long, but it's not a traditional visa but rather an electronic authorization that came into effect recently. Make sure you do it with plenty of time before November to avoid surprises at the airport.
Don't make the trip without thoroughly checking the current requirements, because things changed quite a bit after Brexit and it's still evolving. You're right to be skeptical about what you read online because there's old information mixed in with new stuff.
A passport is enough, that's confirmed. But what you might not be clear on is that the ETIAS mentioned above isn't optional or something you can put off: it's an online authorization system you need to sort out before you get on the plane. It's not a traditional visa, but without it they won't let you in. The process is relatively quick (normally it gets sorted in a few days, though it can take longer), it costs a few euros and you do it from any computer. I'd recommend doing it with time to spare because if you're traveling in November and you wait until the last minute you risk running into problems.
The safest thing is to check the official UK government page or the ETIAS portal directly, either before you buy your tickets or once you have them confirmed. Everything's up to date there with no confusion. Don't rely just on forums or blogs because it changes frequently and nobody wants surprises at immigration.
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