Sheffield, a city in northern England, is about 3 hours from London by train. If buy the tickets in advance, on the National Rail site, you can get good prices, but you have to be sure that you can travel at the particular time. Your ticket will not be valid on later trains. The station was formerly known as Pond Street, Sheffield Midland, referring to the area. You're still in England, so it's worth using discount cards. You can get a 30% discount on all trains if you travel after 9.30am. The station is connected with London St Pancras, which (from a year ago) is also the Eurostar station. If you visit the travel center you can buy, along with your train ticket, a PLUSBUS PASS which is a travel card allowing you to take all the city buses for a day.