What are the differences between US and UK flour?

This is a fascinating topic. I lived in London for a year (but I wasn't baking then) and I had no idea there was a difference (the potatoes, on the other hand I did notice -- no russets!). I checked out British baker Ravneet Gill's recipes (she authored the NYT's "perfect chocolate chip cookie" recipe) and for her British cookie recipes she always uses plain flour (https://www.theguardian.com/food/2020/nov/07/macadamia-triple-choc-and-oats-ravneet-gill-cookie-recipes). For a pie crust, she calls for strong white flour, which is bread flour: https://www.bbc.co.uk/food/recipes/cherry_pie_78840

This post about the best bread flours (https://loafybread.com/best-bread-flour-available-in-the-uk) recos Matthews Strong White Flour (https://cotswoldflour.com/products/matthews-strong-white-flour) as a good all-purpose flour that's available in Tesco, which you'll find everywhere.

So curious how your substitutions and adaptations are going!

The differences between US and UK flour can affect your baking results. US flour is made from hard wheat with higher protein content, while UK flour is made from soft wheat with lower protein content. The protein in flour contributes to gluten formation, which affects the texture of baked goods. US flour produces stronger gluten, resulting in chewier textures, while UK flour produces weaker gluten, leading to softer and crumblier textures.

Since you've moved to the UK, your usual baking recipes may not work as expected. Biscuits and pancakes might turn out flat because UK plain flour has lower protein content, leading to weaker gluten formation. To compensate, you can use a combination of UK plain flour and self-raising flour or add baking powder. Cookies may be puffy and crunchy instead of chewy due to the lower protein content in UK flour. Adding cornstarch or using a mix of UK plain flour and bread flour can help achieve a chewier texture. The pie crust may be too soft to roll and lift because of the weaker gluten formation in UK flour. You can try using a combination of UK plain flour and US cake flour or chilling the dough thoroughly before rolling.

Camille Jones -

From your reporting of making your US recipes in the UK with UK flour, it sounds like the UK flour is softer (has less protein) than that commonly sold in the US.
Found an article that confirms this.
https://thegreatbake.com/all-purpose-flour-uk/

Here are some possible ways to get good results from your homemade baked goods while in UK
1) investigate whether there's some flour with higher protein on sale in UK (specialty shops? health food stores?),
2) find a protein boosting product (if such exists) and add it to the usual British flour on offer,
3) use baking recipes NOT from your US experience, but ones developed in the UK for their available products. A few very reliable authors (if you want some recommendations) are Elizabeth David, Delia Smith and Mary Berry.
Good luck, and maybe tell us some stories after you figure it out!
Nancy