THE weather may be getting daily colder, but Brexit is definitely hotting up.

In the last 24 hours, the British and EU negotiators appear to have reached a deal on the divorce bill for UK withdrawal.

This has ballooned from an initial offer of €20bn to €50bn, although the figure has been left deliberately opaque by both sides.

Rather than produce a number which would inflame Theresa May’s backbenches and make negotiations even harder, the UK will honour a suite of liabilities accrued over four decades, to be paid for years to come.

It is heartening to see some progress after so many months of dithering, but the UK government deserves little credit.

Eight months after triggering Article 50, its main achievement to date appears to have been giving the EU what it wanted all along.

Mrs May’s government has been simply outplayed.

The divorce bill squared off, or least sufficiently fudged, there remain two outstanding issues before the EU will agree to moving on to the second phase of talks on trade and the transition period.

The role of the European Court of Justice in safeguarding the rights of EU citizens in the UK had been thought close to resolution, but the European Parliament’s Brexit point man Guy Verhofstadt now says it is faltering again.

After that there is the far tougher problem of avoiding a border between Northern Ireland and the Irish republic, now the main obstacle to a final agreement between the UK and EU.

Events should come to a head on Monday when the Prime Minister presents the UK’s offer on the three points to European Commission president Jean Claude Juncker in person.

If there is agreement, the matter could be signed off by European leaders in mid-December.

If not, the UK’s next chance to move on to trade will be March.

Despite the desperately tight timetable, EU chief negotiator Michel Barnier appeared rather optimistic in Berlin yesterday, saying he expected to announce progress within days.

But as Brexit moves forward, so the pushback grows more intense.

Labour have tabled an amendment to the Brexit legislation which, if passed next week, would bring outside scrutiny to the divorce bill and give MPs a vote on it.

Meanwhile, in Scotland, two Green MSPs and an SNP and a Labour MEP last night took the first step in an attempt to scupper Brexit altogether.

They hope to use a judicial review to ask the Court of Justice of the European Union to rule if Article 50 can be revoked.

There has never been a definitive answer, although its architect, Lord Kerr of Kinlochard, believes it can be.

If the court agreed it was revocable, it would not end Brexit there and then, but it would create an escape hatch if public opinion shifted decisively against it.

This week’s belated development on costs is welcome, but it should not obscure the fact that this will be a long, hard winter for the Brexit process, and there will be thin ice on every side.