Shadow Business Secretary Chuka Umunna said writing a "blank cheque" for the HS2 project would be irresponsible:
Lots of business people have raised HS2 with me. As I've said, we're in favour but it wouldn't be responsible to write a blank cheque for it
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It is unclear what their alleged plans were.
Anti-terror police are currently questioning the men who were arrested at three separate locations in France.
A weather warning is also in place for Scotland, which could see "treacherous" and blizzard-like conditions on Thursday.