And so it seems that the brexit process again finds itself in a pregnant pause, with both sides still tantalisingly unable to make the substantive move that will kick the talks into their final, decisive phase.

This weeks talks in brussels are the last formal round of negotiations in the diary beyond this week, there is no formal script or choreography in place for what comes next in the precious two weeks between now and the october 15 european council.

Tomorrow we will find out whether both sides have agreed enough to warrant descending into the tunnel (or the submarine as someone in brussels is calling it) that dark, enclosed space where both sides stop leaking and posturing and get down to business.

In brexit negotiations these past four years, the sound of silence has always been the sound of deals being done. eu and uk officials close to the process who are happy to guide and explain their side of the argument all suddenly clam up. thats when you know were close.

So if tomorrow both sides are still publicly waving pieces of paper at each other, pointing to each others mandates and published policy statements, that will be a fair indication that things have gone badly. that the gap is still too wide.

If on the other hand the briefings are bland and somewhat opaque, that is a fair signal that a tunnel is close and that both sides are preparing to make compromises that they would rather not advertise.

Boris johnson needs to manage expectations among his hardline backbenchers; michel barnier has to manage tougher member states, such as france, which still demand that he hold the original line on fish and the level playing field.

The soundings from brussels this week, it must be said, have not been very positive, even if the noises in whitehall are more so, with some insiders talking up the prospects for a deal but that remains some way off.

The british side submitted several working papers last weekend but the european commission told member states that there really wasnt anything new in them. we are still waiting for the beef, said one eu official gloomily.

But that, of course, is part of the problem. the talks remain still stuck in a waiting for godot-type limbo, with both sides accusing the other of being unwilling to make the big first move (for more samuel beckett references see this insightful piece by anton spisak on where a swiss-style compromise might lie on the vexed subsidies question).

The briefing has dwelt in detail on state aid and subsidies in recent weeks, but it remains the issue that turns the key on a wider agreement and which simultaneously unlocks two of the big issues with the northern irish protocol (state aid and tariff payments) that london is legislating to overwrite.

Because if the uk (not surprisingly) rejects as intolerable the eu opening position that the envisaged partnership should ensure the application of eu state aid rules to and in the united kingdom, the spotlight must logically fall on the uks domestic subsidy regime.

The beef that the eu talks about is the uk setting out three things. first, to what extent the uk government is prepared to sign up to shared principles on subsidies in the text of the fta; second, the nature of the uks domestic regulator; and, third, how a dispute resolution mechanism will operate.

It is the second of these the uks regulatory regime that looks to hold the key. as we revealed in july the hardliners, including dominic cummings, want a light touch regime with a vague and non-statutory watchdog-type regulator.

Other more moderate forces in government, including some inside the treasury, seem to see the need for a more toothsome regulator to make the uk market operate smoothly, with an ex-ante function that enables subsidies to be assessed and if necessary blocked before they are doled out.

That is probably still a big stretch for no 10, but building a deal around a uk regulator that has only ex-post powers is going to be much more difficult, though perhaps not impossible with the right supporting architecture. but this is the blockage.

A three-pillared deal could almost certainly be built around an agreed set of principles fleshed out in the fta text; separate eu and uk regulators with ex-ante powers, in which companies from both sides have standing; and a dispute resolution mechanism to resolve differences on whether any countermeasures are fair and proportionate.

The key point for the uk, says james webber, a partner at shearman & sterling, who has written a draft text of a deal acceptable to brexiters, is that the uk and eu regimes are fully independent of the other, but with both sides having legal standing in each others wholly domestic systems.

For its part, the eu has to accept (and this will not be easy) that the uk has gone its own way by voting to leave the eu and when it comes to eu-uk trade, any dispute must be based around measurable impacts on such competition and trade. in short, the eu cannot be in a position where it indirectly expects to dictate uk subsidy or fiscal policy.

An eu exit strategy or xs meeting originally planned for monday to discuss possible concessions by the inner brexit cabinet (johnson, sunak, raab, patel, gove, truss, braverman) was shelved, raising further questions in brussels about whether the uk is willing to move far enough. and time is ticking.

All of which is to say, the deal will be difficult for both sides but it is absolutely there to be done.

Bar chart of estimated % of foreign inputs in uk goods (2016) showing rules of origin

There was a telling moment this week when it emerged that david frost had written to uk auto manufacturers to confess that the eu was not going to grant the uks request for preferential access to the eu single market.

The uk had asked that its carmakers should be allowed to count japanese or turkish car parts as uk-origin, in order for them to meet the requirement that cars should be 45 per cent locally made to qualify for zero-tariff access to the eu under a trade deal but the eu has rejected the request.

As the chart shows, uk manufacturing is heavily reliant on intermediate inputs, which means manufacturers and exporters are vulnerable to the effects of rules of origin requirements (the food and drink industry is in the same boat as autos see this excellent global counsel report on the hidden hard brexit).

The basic point perhaps not widely enough understood is that even if both sides agree to a zero-tariff trade deal, many sectors will struggle to take advantage of that zero-tariff access.

That, in turn, will play into political calculations. out on the stump in 2019, mr johnson promised that its all protected from the point of view of big motor manufacturing investors in our country, but the very skinny deal being negotiated falls short of that promise.

In 2016, mr johnson branded david cameron and fellow remainers as the gerald ratners of uk politics for selling a crap deal as something sparkly and worth having. the risk is that the prime minister, having hailed a deal this autumn, finds that charge laid at his own door.