In the same speech that I mentioned the other day, President Macron noted that

Since 1995, France and the United Kingdom, Europe’s only nuclear powers, have clearly stated that they can imagine no circumstances under which a threat to the vital interests of one would not constitute a threat to the vital interests of the other.

I want today to formally reiterate that assessment. The high level of mutual trust, enshrined in the Lancaster House Treaties in 2010, the 10th anniversary of which we celebrate this year, is reflected in our daily and unprecedented cooperation on nuclear issues. We will steadfastly maintain this cooperation and Brexit will have no impact at all in this regard.

More from the UK on the Lancaster House Treaties.