Nicola Sturgeon's Brexit adviser told us why her single market plans are 'politically, technically and legally' unviable
Speaking to Business Insider on Tuesday, Charles Grant, director of think-tank Centre for European Reform (CER), praised the Scottish government for the "weightiness" of the proposals, but said any special deal is unlikely given the lack of appetite from Westminster, the likelihood of a Spanish veto, and the legal difficulties of such an arrangement.
He said: "Obviously they would be politically, technically, and legally very hard to make work."
"Mrs May would have to push for a deal herself. She would have to say to our partners, 'We want you to give Scotland a sweetheart deal.'"
"I don't think she wants to do that, because she is keen on the integrity of the United Kingdom, and creating differences between England and Scotland isn't what a Tory politician like Mrs May thinks of."
Grant said that the second principal difficulty of Sturgeon's proposal would be objections from UK's European partners.
"They believe the building bloc of the EU is the nation state," he said.
"There isn't any provision in the EU's governance for de facto treaties which give regions a special status or standing within member states, or indeed states outside the EU. The Spanish - and a number of others - are very sensitive on regional questions. Anything that could encourage the Catalans to think they could have special treatment themselves would be seen as a bad thing by the Spanish government."
Technical difficulties
The third problem, Grant said, would be the large technical difficulties that would arise from Scotland remaining in the single market while the UK was outside. "You'd have one set of regulations in Scotland and one set in England - what does that mean for trade between England and Scotland?"
"It would be very confusing for businesses to have different regulations, and possibly different sets of competition policy jurisdiction. What happens if a company is partly English and partly Scottish? There would be enormous technical difficulties.
"Maybe you could overcome them, but you could only overcome them if there was a strong consensus in Edinburgh, London and Brussels that a solution should be found - and I don't see that kind of consensus."
Border controls
Grant also suggested that a single market deal for Scotland could lead to customs controls on the English-Scottish border.
Sturgeon dismissed the idea at a press conference on Tuesday by citing the case of Ireland, and said: "Talk of a 'hard border' for Scotland has always rung hollow from a UK Government that says no such 'hard border' will be required between a post-Brexit UK and the Republic of Ireland, a continuing member of the EU."
Grant believes, however, that there will have to be an intra-Irish border. He said: "I talked to some of the officials involved. She's right that the British and Irish governments are determined to find a way of avoiding customs controls on the border between the north of Ireland and the south, but they haven't found a way yet. I think it's going to be very, very difficult for them to do that.
"I think it's going to be very, very difficult for them to do that.They may be soft controls, but I think there will have to be some controls," he added.
Grant said a similar system would likely apply to to the English-Scottish border. He said that the controls could be "light" rather than "hard," similar to the border arrangement between Switzerland and France, but there was nonetheless the risk of a system which would require paperwork and delays for cars and lorries on the border.
Theresa May told MPs today that she would "carefully consider" Sturgeon's calls to remain inside the single market. However, a spokesperson for the prime minister indicated yesterday that any final deal must apply to the whole UK, which suggests regional access to the single market is unlikely.