I had a look out of curiosity. The book has:
>“In the summer of 1812 there were no fewer than 12,000 troops in the disturbed counties, a greater force than Wellington had under his command in the Peninsula.”
But for that year Wikipedia has
>Wellington's 48,500-man army... https://en.wikipedia.org/wiki/Battle_of_Salamanca
If I remember correctly it was true for a short time when it was compared to a small expeditionary force, that quickly grew. That is why its cherry picked.
The point being made by use of colorful anecdote is however that industrialisation led to internal unrest which required considerable force to manage, and whose ultimate outcome (unprecedented rise in living standards) is much preferable to it being stopped in its tracks. A story that repeats itself again and again, check the American longshoremen union for an especially crass recent example of it.