When Elizabeth II became Queen in 1952, Stalin was still leader of Russia and Truman was President of the USA.
The British Empire, although severely dwindling, still existed. India had become independent just five years before. The British Empire finally ended in 1997 when Hong Kong was given back to China.
The 89 year old head of state, surpasses the reign of Queen Victoria, who until her death in 1901, was Queen for 63 years, 7 months, 2 days.
Wishing Her Majesty many more happy years.