If you take the Eurostar from London to Brussels, you can catch the ICE or Thalys from there to Cologne. From Cologne you can travel to Berlin, Hamburg, Frankfurt, Munich and most other major German cities. You can also catch the occasional ICE train from Brussels and Amsterdam. You will be able to catch the ICE train from London from 2013 when the European rail network is de-regulated. This means that you will then be able to travel to Berlin, Frankfurt and other destinations without changing trains at all, which will be fantastic.
Since June 2007, the ICE trains have run from Paris to Frankfurt, while the TGV runs from Munich to Paris via Stuttgart.
If you can book directly with the Deutsche Bahn, or if you are based in the UK, the favourable option is to book with Rail Europe, who will not only give you a £6 discount if you book online, but will post the tickets to you securely.
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