The fastest way to travel to Windsor Castle from London is to take the train from London Paddington Station to Windsor Central Station. Paddington Station is serviced by the Circle, Bakerloo, District and Hammersmith & City underground lines, making it very accessible from any Central London location.

There are two main options for reaching Windsor from London, depending on your starting point. London Paddington is generally considered the "best" and most frequent route; you take a fast train to Slough and then a quick 6-minute branch-line connection to Windsor & Eton Central. This station is located directly across from the castle walls, putting you in the heart of the town immediately. Alternatively, you can take a direct, slower service from London Waterloo to Windsor & Eton Riverside. This journey takes about an hour and involves no changes. While the Riverside station is slightly further away (about a 5-to-10-minute walk uphill to the castle), it is often the cheaper option and preferred by those who want a guaranteed seat without the hassle of a platform change at Slough.