Last Wednesday a letter written by the International Trade secretary was leaked to Business Insider. In it Liz Truss expressed concern that the UK was not preparing adequately for exiting the EU transition period.

She wrote that the current HMRC proposals to apply the EU tariff as a default to all imports into Northern Ireland from the rest of the world “may call into question NI’s place in the UK’s customs territory” and suggested that the UK could be liable to a challenge at the WTO because it planned to temporarily give the EU preferential treatment.

If full border checks for EU-GB goods are not in place and there is no trade agreement, she believes under WTO rules there could be a case for other countries claiming the UK was illegally treating the EU favourably (and themselves unfavourably) under ‘Most Favoured Nation’ rules.

Truss’s letter was addressed to the Chancellor, Rishi Sunak, and the Cabinet Office minister, Michael Gove. It was also copied to the Home Secretary, Priti Patel. So how did it get into the public domain? I’m told that Liz Truss believes Downing St. leaked the letter in order to undermine her, calculating that it would be assumed she was the leaker.

Whether or not this is true, or whether Truss leaked the letter herself, it is a measure of the growing distrust felt by the Trade Secretary towards those close to the Prime Minister.

DEFRA Minister George Eustice along with his former boss Michael Gove are widely perceived to be the main cabinet opponents of Truss’s free-trading approach to striking post-Brexit trade deals, particularly because of the possible consequences for British agriculture.

Michael Gove is close to both the Prime Minister and Dominic Cummings who was previously Gove’s Spad. The Cabinet Office, seen as the unofficial ‘Department of the Prime Minister’, is geographically next to Downing St. and can be accessed by No. 10 staff without setting foot outside.

The dispute is a matter of policy, rather than personalities. Many Brexiteers privately fear Gove has gone slow on post-Brexit border control preparations in order to maintain high alignment with the EU. They see Truss as the Brexiteer victim of a coordinated protectionist assault.

The enigma at the heart of this clash is the Prime Minister. What does he think and whose side will he come down on?