Q: What is the row about?
A: France is angry 100 small boats wanting to fish in UK and Jersey's rich coastal waters have been refused licences.
It accuses Britain of breaching its trade deal with the EU by refusing to grant better access.
No 10 says some boats don't qualify as they can't prove a history of fishing there pre-Brexit.
Q: What is France threatening?
A: Ramping up customs checks to disrupt cross-Channel trade and banning UK trawlers from landing catches at French ports from tomorrow, and hiking the price of the electricity it supplies for Jersey.
Q: What happens next?
A: No 10 says President Macron's threats would breach the deal and is ready to sue the EU if he presses ahead.
It may trigger sanctions against the bloc. Talks to break the deadlock continue.