Begrudgingly

"Although British involvement in the slave trade prior to 1807 cannot be denied, or its effects diminished, it is also a fact that the Royal Navy was pretty much the only force in the world in the 19th century with the numbers, drive, willingness, firepower, and capability to curtail the global slave trade, and that, without these efforts, many more would no doubt have been taken to slave plantations and other such destinations during the 19th, and possibly even into the 20th, centuries, as it must be remembered that a great many European powers would only begrudgingly commit to ending the slave trade when the other option was continuous war with the British Empire."