He freed his slaves in his will and disapproved of slavery.

ECONOMIST: Washington vanishes

He was an economic liberal who freed his own slaves, but a political conservative.

ECONOMIST: Venezuela's president rewrites the history of his hero

And he did so in 1837-8, just as the West Indies slaves were being released (technically freed in 1833, they were forced to serve an "apprenticeship" which effectively kept them in bondage till 1838).

BBC: Darwin's twin track: 'Evolution and emancipation'