Are you certain they only require the bar code and passport? I believe they require all the documents you have scanned and uploaded. Hence copies of original documents need to be notorized and original documents are not returned.
Not sending the original documents would mean documents could easily be altered using a PDF editor and opening themselves up to the biggest fraud ever.
the UK consulates are a little misleading on their front pages lol
They say visas are usually issued in an hour. What they really mean are tourist visas are issued in an hour and Non Immigrant visas in an hour, once the Non Immigrant application has been pre approved in London.
I don't know of anybody personally who has applied but the requirements are here. Note there are 4 different sets of requirements depending on reason for the visa.