The two men travelled home separately. Speke returned to London first and presented a lecture at the Royal Geographical Society, claiming Lake Victoria as the source of the Nile. According to Burton, Speke broke an agreement they had made to give their first public speech together. Apart from Burton's word, there is no proof that such an agreement existed, and most modern researchers doubt that it did. Tim Jeal, evaluating the written evidence, says the odds are "heavily against Speke having made a pledge to his former leader".