A memorandum read by a long-lens camera as it was carried by a senior Conservative Party aide has suggested Britain is "unlikely" to be able to remain in the single market once it leaves the European Union.
The handwritten note was caught as Tory vice-chairman Mark Field and his aide left a meeting with the Department for Exiting the EU at 9 Downing Street.
It said: "What's the model? Have your cake and eat it."
The memo goes on to reflect on the difficulties the Government faces after it begins the formal two-year process of EU withdrawal when it triggers Article 50 next year.
"Difficult on article 50 implementation - Barnier wants to see what deal looks like first," it noted in a reference to the lead EU negotiator Michel Barnier. "Got to be done in parallel - 20 odd negotiations. Keep the two years. Won't provide more detail. We think it's unlikely we'll be offered Single Market."
The note appears to suggest a transitional arrangement which would allow the UK continued access to the single market after Brexit while it negotiates a new trade deal is also unlikely.
"Transitional - loath to do it. Whitehall will hold onto it. We need to bring an end to negotiations," it said.
It also suggests that a deal on manufacturing should be "relatively straightforward" but admits that services are harder.
The aide carrying the note was identified in press reports as Field's chief of staff Julia Dockerill. She is the latest in a growing list of visitors to Downing Street to be embarrassed after documents they were carrying were picked up by the cameras.
The exact significance of the comments is unclear - although that is unlikely to stop speculation on the implications, given the lack of publicly announced detail about the Government's negotiating strategy.
Field does not have any official role in the negotiations but, as the MP for the Cities of London and Westminster, he is likely to take a close interest in the impact on the City.