The correct answer is false.
It is false that despite the efforts of British abolitionist, the British remained the nation most in favor of slavery.
It was the British government the one that abolished the slave trade that sometimes it allowed. In the 19th century, Great Britain initiated one of the most important anti-slavery movements in Europe, after having allowed it in the 18th century. From 1787 to 1807, the British tried to end the slavery trade. In May 1787, the Society for the Abolition of Slave Tarde was founded. It was an important step to the elimination of this horrible practice. That is why it is false that despite the efforts of British abolitionist, the British remained the nation most in favor of slavery.