Donald Trump is going to be president. Trump was pro-Brexit and will want Brexit to succeed. Furthermore, he wants to replace US trade deals with low-income countries such as Mexico, which he regards as providing a low-wage threat to US jobs, with new trades with higher-income countries such as the UK. He has no interest in TTIP any more and precious little in the TPP. Lastly, US voters are very much in favour of a trade deal with the UK, which makes such a deal easy to get through Congress (the usual obstacle to US trade deals).

All of these factors mean Trump will want a trade deal with the UK. And he’ll want it early. The Republicans controls both chambers of Congress for the next two years. The nature of the cycle means they are likely to do even better in the Senate next time, but recent experience tells us we should not assume apparently obvious political outcomes will come to pass. He has this window of opportunity. He’ll want to cut a deal. It’s also worth emphasizing that Presidents typically aim to establish much of the key elements of their programmes over the first few months they are in office.

So, some time between February and August this year will be the appointed hour. The UK can get an early trade deal with the US, but if we want it we’ll have to take it then. If we can’t take it then, Trump will move on to other things and it could be years – perhaps up to a decade – before the US will get around to wanting to agree a deal with us again.

So, of course, we should take the deal. The only problem is that, as matters stand, UK government lawyers are advising ministers that it would be illegal for the UK to negotiate post-Brexit trade deals before it leaves the EU and that UK ministers are accepting (a) that that is in fact right; and (2) that if it’s true that negotiating such deals is illegal, that can’t be changed or got around.

I think it’s not true that the UK negotiating post-Brexit deals before we leave is illegal, under the Treaties. But, even more fundamentally than that, I think that if it were indeed illegal, UK ministers should not accept that as a settled reality. I agree with Lord Owen that the UK’s being able to negotiate its own post-Brexit deals should be considered non-negotiable and indeed should be considered a deal-breaker for the use of the Article 50 process.

If China told Japan it was forbidden from doing a trade deal with Australia, we would rightly regard that as a “hostile act”. But somehow if the EU did that we seem to think it would be okay? If it’s currently illegal for the UK to negotiate its own post-Brexit trade deals, then we should consider it absolutely imperative that we either change that law or that we get permission, under that law, from the EU to do our own deals. (Note that the EU has given such permission before, in the case of the transitional arrangements for investment agreements at the time of the Lisbon Treaty, so the principle is well-established.)

There should be absolutely no question of our mutely accepting that we aren’t going to negotiate our own deals. The position should be that, of course we are going to negotiate, sign and ratify our own post-Brexit trade deals starting now, and if some paperwork needs to be done to make it legal for us to do that, then someone needs to get on and sort that paperwork out. Our not negotiating such deals should simply not be an option.

Up to now, the UK government has been far far too passive on this. Trump becoming President means we can’t wait any longer. Sort it out, and get on with negotiating and ratifying a deal with the US whilst the deal is there to be done!