Anglo-Chinese Convention Relating to Sikkim and Tibet, which Tibet disregarded since it was for "Lhasa alone to negotiate with foreign powers on Tibet's behalf". The British concluded in 1903 that Chinese suzerainty over Tibet was a "constitutional fiction", and proceeded to invade Tibet in 1903–04. The Qing began taking steps to reassert control, then invaded Lhasa in 1910. In the 1907 Anglo-Russian Convention, Britain and Russia recognized the Qing as suzerain of Tibet and pledged to abstain from Tibetan affairs, thus fixing the suzerainty status in an international document. After the Qing dynasty was overthrown during the Xinhai revolution of 1911, the "amban" delivered a letter of surrender to the 13th Dalai Lama in the summer of 1912. The Dalai Lama expelled the "amban" and Chinese military from Tibet, then all Chinese people, after reasserting Tibet's independence on 13 February 1913.