This is from the London Embassy website:
"Question 1. Do I need a visa to come to the UK?
Probably not. Most U.S. citizens seeking to enter the UK for tourism need only to present a valid U.S. passport. However, you may need a visa, if you have ever applied for and been refused a visa to the UK, been denied entry to the UK in the past, have any criminal convictions in any country or have previously violated the terms of a UK visa. You should visit the UK Border Agency website if you need information about applying for a visa. "
What they are talking about here is an actual visa in your passport, which is applied for in advance. So while people from certain countries do not need to apply for a visa in advance of travel, they are still issued with one at the border when they enter the UK.
This visa will be a stamp in their passport... and although it's just a stamp and not a proper visa sticker, it is still technically a visa for the UK, because as I said, there is no 'visa waiver' for the UK - that is a US program, not a UK one.
The other difference is that an advance-issued 6-month visitor visa is multiple entry, while a 6-month visitor visa stamp issued at the border is only single entry, so if you leave the UK, it becomes invalid and you have to 'apply' for another one to get back in again.
Well, I've been refused once back in May. But if they approve me this time around, on the same visa that I applied for, does it mean I have to apply for visa each time I try to enter the UK? I visit the UK fairly frequently before I got refused using my US passport with no visa. And we plan on visiting UK at least twice a year once my husband move to the US in the near future.
Yes, as you have now had a visa refusal, you should not attempt to travel to the UK again without applying for a visa from the US in advance. So, you will need to apply for a new visa every single time you wish to travel to the UK from now on.
You can attempt to enter without applying for one, but chances are that because you have a visa refusal, you will be refused entry to the UK and sent right back to the US on the next plane.
As it says on the UKBA website:
Check if you need a UK visa
What passport do you have?
USA
What are you coming to the UK to do?
Tourism, including visiting friends or family
You won’t need a visa to come to the UK
However, you should bring the same documents you’d need to apply for a visa, to show to officers at the UK border. (this is what I mean by 'apply' for a visa at the border - you may be asked to provide all the documents you would send for an advance visa application because you still have to prove you meet the visa requirements as a visitor)
You may want to apply for a visa if you have a criminal record or you’ve previously been refused entry into the UK.