The pound rose sharply following a High Court decision that saw campaigners win a landmark battle over Theresa May's decision to use the royal prerogative to trigger Brexit.
The ruling saw sterling shoot past 1.24 US dollars, up nearly 1% on the day.
Three senior judges ruled the prime minister does not have power to use the prerogative to trigger Article 50 of the Lisbon Treaty to start the UK's exit from the European Union - without the prior authority of parliament.
Neil Wilson, markets analyst at ETX Capital, said: "Most MPs are natural Remainers, although they would face intense pressure from constituents to deliver the referendum mandate."
Mr Wilson added that the decision is a "body blow" for Mrs May.
"The High Court ruling on Article 50 is a body blow for Theresa May and the Brexit-leaning ministers at the heart of government. It's made triggering Brexit a lot trickier and has given sterling a massive shot in the arm.
"The stage is now set for a fresh battle over Brexit and there is the prospect that parliament will block Britain's withdrawal from the EU, albeit a dim and distant one for now. We need to get more clarity on what MPs think and intend to do about this now they have a say."
