Speke was much attached to Bombay and spoke highly of his honesty and conscientiousness. Bombay's efforts in dealing with hostile tribes, interpreting and keeping the safari crew on track, was a great help to the expedition. Less is known of Mabruki, the other caravan leader, but he was later known as Mabruki Speke, and like Bombay became one of East Africa's great caravan leaders and was also a member of the Yao tribe like Bombay. Because of Speke's recommendations, both Bombay and Mabruki served on Henry Stanley's 1871 expedition to find Livingstone. Return to England and debate over the source of the Nile On 26 September 1858 the return journey from Kazeh was started with 152 porters; both men had to return as their military leaves were coming to an end, although Jeal contends that they could have extended the trip by asking for an extension, as their clear mission statement of the Royal Geographical Society (RGS) was to find the source of the Nile. The expedition had lost a great many people through desertions, disease and hostilities, but in Kazeh, on the return journey, Mabruki had recruited local porters. Again Speke and Burton suffered from severe illnesses and had to be carried in a litter (machilla) by the porters some of the way. Once Speke and Burton were back on the coast they went by ship to Zanzibar and then travelled to Aden. When back at the coast Burton had written a letter to Norton Shaw of the Royal Geographical Society (which had partially sponsored the journey) in which Burton enclosed a map of Lake Victoria made by Speke and wrote "there are grave reasons for believing it (the lake) to be the source of the principal feeder of the White Nile." Now further disagreements developed; Burton maintained that they had promised each other in Aden not to make public announcements till they both were back in England and Burton accused Speke of a breach of promise for publicly claiming that the source of the Nile was found on their trip. Burton now turned against the theory that Lake Victoria was the source of the Nile (and now said the river flowing out of the north side of Lake Tanganyika was the source) and thus also reversed himself from the position he took in the letter to Norton Shaw. In that same letter to Shaw, Burton had also stated