Potted Plant

From a placard:

"The World's Oldest Potted Plant? This plant (Encephalartos Altensteinii) has lived through Kew's entire history as a botanical garden! Collected by Kew's first plant-hunter, Francis Masson, it left the shores of the Eastern Cape in South Africa in 1773 and endured a long ocean voyage before finally arriving in Kew in 1775. This plant flourished as the French Revolution raged, while Trevithick invented the steam locomotive, and Armstrong walked on the moon. It was one of the first plants to be moved into the Palm House in 1848."

The plant also there during the American War of Independence (1775-1783) but I might not include this, either, if I was British. By birth, that is.