Hilary Benn: 20 months in, we still don't know how Prime Minister plans to square circle
As we mark the first anniversary of the triggering of Article 50, the road towards Brexit is still shrouded in fog and uncertainty.
With just 12 months to go, we still do not know what our future economic relationship is going to be because we have only just begun to talk about it with the EU.
Nowhere will that relationship have more consequence than on the border between Northern Ireland and the Republic.
We all know how important our shared membership of the EU was to the crafting of the Good Friday agreement, and none of us want to see the peace and stability it has brought put at risk.
So the future of the border is not just a matter of economics; it is about something much more. As Peter Sheridan of Co-operation Ireland put it so eloquently: "After the Good Friday agreement, you had this idea of a region whose inhabitants could be British, Irish, or both."
Just before Christmas, we visited the border at Middletown between Armagh and Monaghan. There was nothing there - that was the whole point - just a road with lots of traffic carrying goods and people on their way to work.
And as we stood there we heard of how 30 years earlier at that very spot there had been checkpoints, a customs post, an army base, a police station and watchtowers.
The Government is committed to keeping the border open - there will be no checks and no infrastructure, ministers say - and we all support this aim.
The question is, how can they ensure this when the UK will be leaving the customs union and the single market?
I think it's very hard to see how these two objectives can be reconciled, and I would like us to stay in a customs union with the EU and stay close to the single market.
The Government knows there is a problem because it has proposed a fall-back in which the UK will maintain "full alignment" with the rules of the internal market and the customs union which support north-south cooperation, the all-island economy and the protection of the 1998 Agreement.
It argues however that this won't be necessary because another way will be found to meet its objective, but 20 months on from the referendum we are still waiting to see what this is and how it would work. It is now clear that negotiating all the things that still need to be sorted out - the future of our trade and services (80% of the British economy is services), vital cooperation on security, defence and foreign policy, working together to make sure our skies, medicines and food are safe and all else besides - will spill over into the transition period that has now been agreed.
But in the meantime, the certainty that the border needs and businesses require remains elusive.
As someone said of Brexit recently, "For something so apparently simple, it's actually very complicated".