Just half an hour from London Paddington to Windsor & Eton Central, via Slough on Great Western Railway. Or direct from London Waterloo to Windsor & Eton Riverside on South West Trains. Approximate journey time from London Waterloo is less than 1 hour.
There is a shuttle bus service to the park from stops close to both rail stations; please note that this is a chargeable service and is not operated by the park.