The UK solved the problem by paying its slave-owning class £20 million in compensation/bribes after abolition - which was 40% of GDP at the time, so the eqv. of roughly £1 trillion today.

I can't imagine the UK agreeing to adopt the South after that, if only because the South might have expected something similar.

Arguably Lincoln could have saved money overall by suggesting the same trick in the US and paying the South to abolish and mechanise. The total cost of the Civil War was around $7bn nominal, which was very close to 100% of nominal US GDP at the time.

Excellent book review, btw.