If you take the high-speed Eurostar from London to Paris or Brussels, from which London terminus will your train depart?
Eurostar is a high-speed railway service connecting London with France and Belgium.
Since 2007, the London terminus has been St Pancras.
St Pancras Station
The other London rail stations mentioned in the question have had a prominent role in providing train services to France, however, they do not currently provide Eurostar services. From November 1994 to November 2007, Waterloo was the London terminus of Eurostar. Many years ago Golden Arrow services to France departed from Victoria. Trains to Dover (connecting to ferry services) are also available from Charing Cross.