“I do not want Britain to be part of the Common Commercial Policy and I do not want us to be bound by the Common External Tariff. These are the elements of the Customs Union that prevent us from striking our own comprehensive trade agreements with other countries. But I do want us to have a customs agreement with the EU. Whether that means we must reach a completely new customs agreement, become an associate member of the Customs Union in some way, or remain a signatory to some elements of it, I hold no preconceived position. I have an open mind on how we do it. It is not the means that matter, but the ends.”
What does that mean in practice? Essentially the Prime Minister is proposing a bilateral customs deal between the UK and the EU, and inviting the Customs Union to change to match it if it wishes. She doesn’t mind if the eventual arrangement retains the name “the Customs Union” and has other members if needs be, but her demand is that for the UK to be a member of the Customs Union, the Union must ditch its distinguishing features. If it prefers not to, we won’t be a member of it and will have a customs deal in another form. So really she is ruling out Customs Union membership, too.