The idea that post BREXIT trade negotiations would be wrapped up quickly is divorced from reality
Table above: Opening excerpt EU Trade deals from 2000 onwards
Alastair Meeks questions the assertions from LEAVE & Grayling
There has been outrage on the Leave side at the suggestion in an official government paper that negotiations after a vote to leave the EU in the upcoming referendum might take up to 10 years or more. Chris Grayling commented: “Claims that it will take twice as long to sort out a free trade deal with the EU as it did to win world war two are clearly ludicrous”.
On this occasion, there is a simple way of testing the claim, which is to look at what has happened in the past. If Britain were to vote to leave the EU, it would be only the third country to do so after Algeria and Greenland, and neither of those cases is comparable, so the negotiations would be breaking new ground. However, the EU is constantly negotiating trade deals of one kind or another, and it is reasonable to assume that the timescales of such negotiations between sovereign countries and the EU are reasonable guidelines to how long such discussions might take.
Somewhat to my surprise, no one seems to have looked at this before. Then I started looking and I realised why. It is usually far from clear when negotiations can be said to have started and in many cases it is far from clear when agreements can be said to have come into force. Often the formal start date of negotiations takes place years after the idea of an agreement had been aired – Kosovo is a good example of this. Often the agreement is brought partially into force on an interim or provisional basis before full ratification.
Anyway, my stab, covering every negotiation completed by the EU or in progress since 2000 (excluding the Economic Partnership Agreements with developing world countries, which are probably not really comparable and which would distort the table by making the EU look still more lethargic) is linked at the top of this thread.
In most cases you could take issue with the dates that I have selected. I have probably erred on the side of brevity rather than length of negotiation, selecting formal dates for negotiations opening when I cannot establish a date that will serve as the real world start point.  I decided to use the date of full implementation, since that will mark the end of the period of uncertainty.
From this you will see that every criticism about the EU moving slowly is abundantly justified. The quickest fully completed negotiation since the turn of the millennium took four years. The average completed negotiation took 7 years 11 months. This average, of course, is biased in favour of the speedier negotiations because the slower negotiations that broke down are excluded on this basis.
Now you might argue that the EU will pay much closer attention to negotiations with Britain on departure than to any others (though you could equally argue that the atmosphere will be poisonous and the negotiations will be of domestic political importance for every negotiating party). You might argue that interim arrangements will be put in place even if they get bogged down. But it seems impossible to me to argue that claims that it will take twice as long to sort out a free trade deal with the EU as it did to win world war two are clearly ludicrous. It seems an entirely plausible outcome based on past experience. And the chances of this being wrapped up in a year or two seem remote.