My parents are going to visit the United Kingdom from South America. I have checked UK's site and they do not need a visa.
Only one requirements is not clear enough to me, and that is whether they ask for proof of where they are going to stay.
Would they be asked for proof of accommodation or just a passport and tickets?
My parents would be staying with me (in the UK), and they don't have hostel/hotel receipts.
That's why I would like to have a clear idea. Also I am not sure an invitation letter would be of any help, since as I said they do not need a Visa.