  The generalised colouring numbers $\mathrm{col}_r(G)$ and
$\mathrm{wcol}_r(G)$ were introduced by Kierstead and Yang as a generalisation
of the usual colouring number, and have since then found important theoretical
and algorithmic applications. In this paper, we dramatically improve upon the
known upper bounds for generalised colouring numbers for graphs excluding a
fixed minor, from the exponential bounds of Grohe et al. to a linear bound for
the $r$-colouring number $\mathrm{col}_r$ and a polynomial bound for the weak
$r$-colouring number $\mathrm{wcol}_r$. In particular, we show that if $G$
excludes $K_t$ as a minor, for some fixed $t\ge4$, then
$\mathrm{col}_r(G)\le\binom{t-1}{2}\,(2r+1)$ and
$\mathrm{wcol}_r(G)\le\binom{r+t-2}{t-2}\cdot(t-3)(2r+1)\in\mathcal{O}(r^{\,t-1})$.
In the case of graphs $G$ of bounded genus $g$, we improve the bounds to
$\mathrm{col}_r(G)\le(2g+3)(2r+1)$ (and even $\mathrm{col}_r(G)\le5r+1$ if
$g=0$, i.e. if $G$ is planar) and
$\mathrm{wcol}_r(G)\le\Bigl(2g+\binom{r+2}{2}\Bigr)\,(2r+1)$.
