Original sentence: However, the Tibetans rejected the results of these negotiations, including the border settlement and the trade agreement.The presence of Chinese ambans in Tibet led the British to assume that China possessed authority over Tibet and they began to negotiate with China regarding relations with Tibet
Edited sentence: The presence of Chinese ambans in Tibet led the British to assume wrongly that China possessed authority over Tibet, and they negotiated with China the Anglo-Chinese Convention related to Sikkim and Tibet.Tibet rejected the results of these negotiations, including the trade agreement, since only Lhasa had the right to represent Tibetan interests with foreign powers