This is false.

The abolitionist movement started in 1787 when William Wiberforce started championing it in parliament and quickly grew traction across the UK.

Britain literally had no choice but to ban slavery there were over a million people in the british isles demanding a full ban on slavery at a time when it had a populstion of 10 million, and they still dragged their feet and did a half measure to ban the slave trade instead as late as 1807. A full 20 years after the start of the movement.

The US banned slavery outright after the civil war

France banned slavery outright before Napoleon took over

Britain did not for another 20 years when the abolitionist movement grew too strong.