Here I am putting that name through a search engine before realising it’s the exact brand of mustard sitting in my cubboard, which I ate for lunch this afternoon. My search is over.

Yeah it's in practically every grocery store where I am in Canada.

80% of Maille’s mustard seeds come from Canada.

according to wikipedia, a long time ago the French makers of Grey Poupon bought out the competing French brand Maille.

https://en.wikipedia.org/wiki/Grey_Poupon#History

For those that like their mustard a little more raw, Maille Wholegrain is my mustard of choice. I keep several others (A deli, a horseradish, a brat) around but that's the true best.

I found that the Maille mustard they sell in the UK is heavily diluted with oil compared to the one in France. In the exact same packaging.