In 1851, when Livingstone finally left Kolobeng, he did not use this failure to explain his departure, although it played an important part in his decision. Just as important had been the three journeys far to the north of Kolobeng which he had undertaken between 1849 and 1851 and which had left him convinced that the best long-term chance for successful evangelising was to explore Africa in advance of European commercial interest and other missionaries by mapping and navigating its rivers which might then become "Highways" into the interior.