On August 14, 1793, the Qianlong Emperor issued an edict. Everyone who came to the court with tribute had to perform the three kneelings and nine kowtows, san gui jiu kou (三跪九叩), even a king in person. The British envoy Lord Macartney refused. In the end, the emperor gave way and allowed him to kneel on one knee, as he did before his own king.
At the audience in Rehe on September 14, Macartney knelt on one knee. Later Chinese records said that he had been so overawed that he fell to both knees. Chinese Wikipedia calls this claim unfounded. One Chinese article holds that he performed the full kowtow at the emperor’s birthday ceremony three days later. The sources still disagree.
In 1816, another British envoy, Lord Amherst, also refused the kowtow. The Jiaqing Emperor expelled his embassy from the country.