Despite a reputation for caution and stability, Theresa May produced a pretty major rabbit from her Brexit speech hat today. Not that Britain would be leaving the Single Market – that has been obvious for some time – but news that the final Brexit deal will be put to a vote in both the House of Commons and the House of Lords.

The significance of this was not lost on the markets – sterling shot up in value, from $1.20 to $1.23.

While the House of Commons may be expected to vote for the deal, upholding the will of the British people, the House of Lords is far less clear cut. Its members were overwhelmingly Remain supporters, and some have been coordinating anti-Brexit efforts for some time.

They would stand accused of ignoring the democratic will of voters – particularly given their unelected status – but here’s their logic: No manifesto has spelt out that a vote to leave would mean leaving the Single Market. Indeed, the Conservative manifesto in 2015 stressed its importance to the UK economy: “We say: yes to the Single Market. Yes to turbo- charging free trade. Yes to working together where we are stronger together than alone.”

Any such stand-off with the Lords could force a General Election, effectively putting the final deal to a popular vote. Edelman’s new data released this week showed UK voters to be overwhelmingly in favour of getting on with Brexit, and that if it were re-run tomorrow, the referendum would still end in a narrow Leave vote. Of course, many other factors would be at play, but both of these suggest a mandate for the negotiated deal.

Edelman has prepared a full briefing document which you can read here or below.