I am a US citizen and I have the opportunity to work for a company that is based out of the UK, but performs most of its business globally and on-site. Most of my contract work for them will be performed in the US, but may also occur in other countries. I will not be moving to the UK and the likelihood of me actually performing work for them in the UK would be extremely rare.
Do I need a special work permit or visa in order to perform work for this company as a freelancer?