A400 v VC10

[Archer]

now then....a high wing aeroplane has more natural lateral stability (because most of the weight is below the wing)..so adding anhedral (which de-stabilises) makes the aeroplane more neutral

That is one reason, the second one is that a high set wing creates changes in local AOA with sideslip. When the nose yaws to the right (or the a/c rolls left, uncoordinated), the flow around the fuselage from the left creates an increased AOA on the left wing and a decreased AOA on the right, causing the a/c to roll right. This is a very positive roll (lateral) stability which designers need to tone down, hence the anhedral. A low set wing works the same but in the opposite directions which is why they need dihedral to make it more stable in the lateral sense.