Each student is responsible for ensuring that he or she has a valid passport. If you do not have a passport or if your passport has expired, you should apply for a new passport or renewal as soon as possible. Information on how to obtain or renew a passport is available at http://www.travel.state.gov/passport/passport_1738.html. Make sure you have a passport that is valid for at least six months after the program end date (i.e., valid through July 2018).
If you are a US citizen or green card holder, YOU DO NOT need a visa to enter the UK. If you are a national of another country, please check with your respective consulate/embassy to find out whether you need a visa or not and proceed accordingly.