If only there was something that would prevent mud and water to be thrown from the wheel. Something that somehow curves over the profile of the tire; sturdy yet light... oh, hang on...
I rode through some water and a bit of dirt recently and not a speck. Anyway, panniers are usually covered in hardy material. Mudguards do protect the pannier to some extent (spray water ricocheting off the rack top) while also not hosing the riders behind me down.
You are possibly looking for something called a "Jasbeschermer", which is what the london hire bikes have on their rear wheels. I'm not sure if there's an English name for them. Good luck finding a vendor of these beasts in the UK, however.
If only there was something that would prevent mud and water to be thrown from the wheel. Something that somehow curves over the profile of the tire; sturdy yet light... oh, hang on...