I had tried a couple of the tools for compiling less on windows, but none seemed to compile bootstrap out of the box.
Instead I found Sylvain’s post which was exactly what I was after.
It was a great post, and I only had to work around one issue:
Step 2.3 is slightly wrong, although the binary is called lessc, in npm it is just less. Therefore the command should be: npm install less
(remove the final c)