However, securing uniform compliance with a total prohibition of slave-raiding, which was traditionally of central importance to the North African economy, presented difficulties beyond those faced in ending attacks on ships of individual nations, which had left slavers able to continue their accustomed way of life by preying on less well-protected peoples. Algiers subsequently renewed its slave-raiding, though on a smaller scale. Measures to be taken against the city's government were discussed at the Congress of Aix-la-Chapelle in 1818. In 1820 another British fleet under Admiral Sir Harry Neal again bombarded Algiers. Corsair activity based in Algiers did not entirely cease until its conquest by France in 1830.