We're heading for a quickie divorce from the European Union – but that's when the problems will really start

Any final deal has to be ratified by 27 EU governments and parliaments and if it includes proposed UK discriminations against citizens of any EU member states it will arouse national political opposition in any EU member states Britain wants to treat differently from others

David Davis speaks in House of Commons about the Brexit white paper (BBC News)

The UK’s goals for the impending Article 50 negotiations with the European Union are clearer now the Government has published its white paper setting out what it wants. In the Commons David Davis confirmed that Britain has no interest in staying in the single market or even partial membership of the EU customs union. It is full political and economic isolationism. Nevertheless fully cutting the UK out of Europe will take well into the next decade.

The German election in September is now the event to watch as, regardless of Theresa May’s White Paper wish list, no real negotiations will start until there is a German government in place and that may not happen until the end of the year.

The timetable goes like this. Once May’s Article 50 notification letter arrives in Brussels next month, it is sent to the 27 remaining EU member states. They will then decide what mandate to give Michel Barnier, the European Commission's chief Brexit negotiator, when heads of government meet at the June EU Council meeting.

The Article 50 negotiations won’t make any progress during the summer break or in the build-up to French and German elections, scheduled for 23 April and 24 September respectively.

No one knows the outcome of the German election. But speaking to German industrialists last month Angela Merkel told them not to play games over Brexit. The German priority is to maintain the single market of 27. Last year the Eurozone grew faster than the US economy and unemployment is coming down. Merkel insisted that there could be no partial, sectorial or special deals for Britain.

As the German foreign ministry’s top Brexit negotiator told me, after Brexit, “Britain becomes a third country “ In that means we have the same status as other nations that want to cut a trade deal with the EU. Other G7 economic powers like the US or Japan have no automatic, unfettered access to the world’s biggest market unless their firms and banks open offices or factories inside the EU not in a “third country” as the UK will become.

After the German election in September there will be a laborious three months of coalition building, party conferences to accept or reject the contract drawn up between the governing parties – whoever they are.

So we have to wait for the appointment of a new German Foreign Minister at the end of the year. Since the German Foreign Ministry is in charge of Brexit negotiations there will be no settled Brexit policy from Berlin. On what the UK has to pay, if hopes that some access for the City is feasible, whether the open border in Northern Ireland or the rights of 10,000 UK citizens in Gibraltar to cross the frontier from Spain every day can be maintained, or whether there can be parallel discussion on a future UK-EU trade deal – for at least 12 long months.

And without a German line there is no EU 27 line. Any final deal has to be ratified by 27 EU governments and parliaments and if it includes proposed UK discriminations against citizens of any EU member states in terms of work, residence or travel visas it will arouse national political opposition in any EU member states Britain wants to treat differently from others.

The withdrawal treaty ratification process needs a minimum of six months before March 2019 when Britain secures political Brexit before the next European Commission, Parliament and Council of Ministers begin work in May 2019.

That means there is a short nine months between January 2018 and October 2018 to conclude the legal language that divorces Britain from Europe. That may be all the negotiators can do – a limited divorce settlement – decree nisi. The final divorce and the future relationship with the continent Britain shares with other nations will take many years with Britain on the outside looking in.

Denis MacShane is a former UK Minister for Europe, His book, Brexit: How Britain Left Europe, is published by IB Tauris.