Your challenge, should you choose to accept it, is to outline a mini-TL where Britain is and remains a reactionary power on the issue of slavery until as close to the end of the 19th century as possible (rather than becoming the kind of country which pressured Brazil to abolish slavery as in OTL). A caveat is that Britain must lose the ARW (or its analogue), so no using keeping the OTL American South to bolster domestic support for slavery in Britain.