To prevent a repeat of this, swift action was taken. Brazil was still one of the largest slave trading nations and continued to defy British diplomatic calls to cease trading. In 1846 Palmerston returned as foreign secretary and in 1850 permitted Royal Naval vessels to enter Brazilian waters in order to blockade slavers on both sides of the Atlantic. By 1852 the Brazilian trade could be said to be extinct. “For Palmerston … the naval campaign on the coast of Brazil had brought the long drawn-out saga of the Brazilian slave trade to a resolution within twelve months.”