Amid the predictable boosterism surrounding the Brexit deal sealed on Christmas Eve, not least from Boris Johnson and senior members of his Cabinet, there is one unarguable fact: it is the first recorded instance of a Prime Minister keeping an election promise.
For that reason, if no other, we should savour the moment when Mr Johnson "got Brexit done", as it is unclear when - or even if - he intends to keep another manifesto commitment.
Some 46 years after we joined the EEC, and over four years after the clear but narrow majority vote in favour of leaving, we now have an untried relationship with our former 27 co-member states.
First Minister Arlene Foster and Deputy First Minister Michelle O'Neill issued a joint statement on the agreement - something they were unable to do about domestic matters only hours previously.
They welcomed "the start of a new era" and underlined the desire to maximise the opportunities for the local economy.
In a separate statement Mrs Foster, as DUP leader, welcomed the "sensible deal" as "the most favourable outcome". In truth, the deal is the least bad option for the UK, including Northern Ireland, as the alternative was a ruinous no-deal.
Finally we have something that gives tangible effect to the popular will expressed in the 2016 referendum. Nevertheless, the agreement comes at a price. The UK will be no longer bound by EU rules and the European Court of Justice, and we will also leave the European Arrest Warrant scheme. However, London has undertaken to mirror many of these regulations in domestic law.
The continuing partnership with Europol will not be as beneficial as if we were a full EU member state, though the UK remains a signatory to the European Convention of Human Rights.
Significantly, the UK failed to persuade the EU to recognise automatically its qualifications for professionals in medicine, law, architecture and other disciplines, and individuals will need to petition the EU for professional recognition.
On the plus side, the Irish Government will maintain access to the Erasmus scheme for students from Northern Ireland.
Overall, while supporters of the deal claim that the tortuous negotiations were justified in restoring the UK's "sovereignty", the coming months may reveal a worrying lack of unanimity as to what that means in practice.
How the agreement credibly reflects the will of the majority expressed in 2016 is anybody's guess.