# Labelling a bar chart with multiple data sets

I'd like to plot a bar chart with two data sets $\{a_1,a_2,\dots,a_n\}$ and $\{b_1,b_2,\dots,b_n\}$ in such a way that the columns appear in the order $\{a_1,b_1,a_2,b_2,\dots,a_n,b_n\}$ and that each pair of columns is labelled with labels $\{\ell_1,\ell_2,\dots,\ell_n\}$.

Here's a fairly minimal working non-example:

BarChart[Transpose[{{1, 2, 3, 4}, {1, 1, 3, 5}}], ChartLabels -> {"A", "B", "C", "D"}]


which plots this

whereas I would like the labels to be A B C D and, if possible, centred under each pair of columns.

Many thanks in advance for your help.

BarChart[Transpose[{{1, 2, 3, 4}, {1, 1, 3, 5}}], ChartLabels -> {{"A", "B", "C", "D"}, None}]

See the ChartLabels section of BarChart for similar tricks.
• Is there a way to do this with just two datasets, wherein there's no particular pairing between the elements as above? I.e., I'd like to have something like two side-by-side datasets, {1,2,3,4} and {5,6,7,8}, with the labels "Dataset 1" and "Dataset 2" underneath each one. – Ben Kalziqi Jun 6 '18 at 21:26