After Richardson met Woodthorpe Charles Clarke, an old friend from Shanghai, they joined fellow merchant William Marshall, and Marshall's sister-in-law Margaret Watson Borradaile to go on a sightseeing ride via nearby Kanagawa town towards the temple of Kawasaki Daishi. While travelling on the Tōkaidō road – the Imperial highway – through the village of Namamugi (now part of Tsurumi ward, Yokohama), the party encountered the retinue of Satsuma regent daimyō Shimazu Hisamitsu (otherwise Shimazu Saburō) heading in the opposite direction. When Richardson approached Shimazu's palanquin too closely, the daimyō's bodyguard attacked the Englishman. Marshall and Clarke were also severely wounded in the incident. Grievously wounded, Richardson fell from his horse a short distance from the attack and was killed with a coup de grâce on the orders of Shimazu. This is known as the Namamugi Affair.
Richardson's grave is in a private plot near to the Yokohama Foreign Cemetery between the later graves of Marshall and Clarke.
Quotes from others about the person
“In a 2013 article, Historian Folker Reichert accused Richardson of cultural ignorance, arrogance, and racism. According to Japanese reports at the time, he disrespectfully rode in the middle of the road and even tried to get between the regent's litter and his bodyguards.
Just before the incident, after having been warned not to provoke the guards, Richardson allegedly said, "I have been living in China for fourteen years. I know how to deal with these people."
Richardson's uncle was reportedly not surprised about his nephew's demise and blamed him for being reckless and stubborn.
Frederick Wright-Bruce, the British envoy to China, remembered Richardson as an arrogant adventurer.”