The Roman Empire lasted around 500 years from the ascension of Julius Caesar to the deposition of teenage ruler Romulus Augustulus.
By this timeline the United Kingdom in its current form is middle-aged, with Ireland joining England, Wales, and Scotland in 1801.
So how long do we have left?
A study part-sponsored by NASA's Goddard Space Flight Center was not optimistic.
Led by mathematician Safa Motesharrei, it questioned the sustainability of modern civilisation.