Bahn Spezial London. If you have bought your ticket and have an allocated seat you have nothing to worry about. Large families, preferential reimbursement or military card), you also get 50% discount on the belgian part of an international journey with intercity or regional trains at standard fare.
However, the db barcodes don't work in the automatic gate scanners so you simply need to check in using the staffed kiosks, not the automatic gates. For a 6:26am direct train, the price on bahn.com is 118 eur. As well as linking austrian cities, railjet runs into neighbouring countries like germany, czech republic, hungary, switzerland and italy.
