  Supposing there exists an effective charge which defines an evolution scheme
for both unpolarised and polarised parton distribution functions (DFs) that is
all-orders exact and using Ans\"atze for hadron-scale proton polarised valence
quark DFs, constrained by flavour-separated axial charges and insights from
perturbative quantum chromodynamics, predictions are delivered for all proton
polarised DFs at the scale $\zeta_{\rm C}^2 = 3\,$GeV$^2$. The pointwise
behaviour of the predicted DFs and, consequently, their moments, compare
favourably with results inferred from data. Notably, flavour-separated singlet
polarised DFs are small. On the other hand, the polarised gluon DF, $\Delta
G(x;\zeta_{\rm C})$, is large and positive. Using our result, we predict
$\int_{0.05}^1\,dx\,\Delta G(x;\zeta_{\rm C}) = 0.214(4)$ and that experimental
measurements of the proton flavour-singlet axial charge should return $a_0^{\rm
E}(\zeta_{\rm C}) = 0.35(2)$.
