Eurostar has revealed plans to run double-decker trains through the Channel Tunnel for the first time.
The cross-Channel rail operator has confirmed it will order up to 50 trains from manufacturer Alstom, eventually increasing the size of its fleet by nearly a third.
The expansion plans would include investing heavily in a crucial London depot, it said.
But questions remain over whether the facility has enough space for both Eurostar and potential rival operators to use it.
In the €2bn (£1.74bn) deal, confirmed on Wednesday, Eurostar has ordered 30 "Celestia" trains, with the option for 20 more.
