The leader in the british abolition movement was mary stewart. frederick douglass. william wilberforce. olaudah equiano.

The correct answer is William Wilberforce.

Mary Stewart was a British novelist who wrote romantic mystery novels during the middle of the 20th century, almost a century after slavery was outlawed.

Frederick Douglass was one of the leaders of the abolitionist movement in the United States, not the United Kingdom.

Equaino was a former slave that wrote about his experiences in a popular autobiography. Even though his book helped aid in ending the British participation in the African slave trade, he was not alive during the abolitionist movement of the early 1800's in Britain.

This shows that William Wilberforce is the only correct answer.