Why does it all have to be so complicated?

"It's OK, we can just walk away with no deal, and trade on WTO terms," they keep telling me.  "Why should Brexit be complicated?"

Well, apart from the fact that the process we're about to enter with the sending of a little Article 50 letter isn't a trade negotiation...

If we walk away with no deal that's no deal on the future rights of British ex-pats in EU countries and other EU ex-pats in the UK.  It means nobody knows the status of the border between Northern Ireland and the South, and poor Nigel Farage doesn't know where his EU pension will come from.  And a few thousand other things.

We already trade on WTO terms with most of the world. We use the EU's terms.  To reactivate the UK's membership of the World Trade Organisation we have to propose a schedule of tariffs and other ways we want to deal with the world.  And any other member of the WTO can object to our proposals.

One of those other members is the EU, part of whose schedule we would probably try to take on, to save time.  Because what we don't have is time.

At the moment we leave the EU we have to know the terms on which we deal with the EU, and "no deal" doesn't sound a good way to start.  We also lose our access to the dozens of trade agreements the EU has made while we've been a member.  Many-to-most of those might be available for quick re-signing, but at least one country has already argued that a lone UK shouldn't just get the same terms as we had while part of a 500million-strong market.

Remember all those other countries queuing up to sign shiny new trade deals with us the moment we leave?  If they have any sense at all, nothing will be finalised until they know our relationship with the EU and so what we're worth to them.  Shall we say "no deal" might well be of less value in some cases?

To say nothing of the things that Article 50 actually does cover - how far do we get without a proper legal relationship with international regulatory systems for air travel, chemicals manufacture, medicines testing and dozens of other sectors?

A lot of these things might well be easy enough to reconstruct - REconstruct, at a cost - but not if we walk out without a deal.