The Royal Observatory, Greenwich (ROG; known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in Greenwich Park in south east London, overlooking the River Thames to the north. It played a major role in the history of astronomy and navigation, and because the Prime Meridian passes through it, it gave its name to Greenwich Mean Time, the precursor to today's Coordinated Universal Time (UTC). The ROG has the IAU observatory code of 000, the first in the list. ROG, the National Maritime Museum, the Queen's House and the clipper ship Cutty Sark are collectively designated Royal Museums Greenwich.The observatory was commissioned in 1675 by King Charles II, with the foundation stone being laid on 10 August. The old hilltop site of Greenwich Castle was chosen by Sir Christopher Wren, a former Savilian Professor of Astronomy; as Greenwich Park was a royal estate, no new land needed to be bought. At that time the king also created the position of Astronomer Royal, to serve as the director of the observatory and to "apply himself with the most exact care and diligence to the rectifying of the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting of the art of navigation." He appointed John Flamsteed as the first Astronomer Royal. The building was completed in the summer of 1676. The building was often called "Flamsteed House", in reference to its first occupant.

The scientific work of the observatory was relocated elsewhere in stages in the first half of the 20th century, and the Greenwich site is now maintained almost exclusively as a museum, although the AMAT telescope became operational for astronomical research in 2018.

Charles II (29 May 1630 – 6 February 1685) was King of Scotland from 1649 until 1651, and King of England, Scotland and Ireland from the 1660 Restoration of the monarchy until his death in 1685.

Charles II was the eldest surviving child of Charles I of England, Scotland and Ireland and Henrietta Maria of France. After Charles I's execution at Whitehall on 30 January 1649, at the climax of the English Civil War, the Parliament of Scotland proclaimed Charles II king on 5 February 1649. But England entered the period known as the English Interregnum or the English Commonwealth, and the country was a de facto republic led by Oliver Cromwell. Cromwell defeated Charles II at the Battle of Worcester on 3 September 1651, and Charles fled to mainland Europe. Cromwell became virtual dictator of England, Scotland and Ireland. Charles spent the next nine years in exile in France, the Dutch Republic and the Spanish Netherlands. The political crisis that followed Cromwell's death in 1658 resulted in the restoration of the monarchy, and Charles was invited to return to Britain. On 29 May 1660, his 30th birthday, he was received in London to public acclaim. After 1660, all legal documents stating a regnal year did so as if he had succeeded his father as king in 1649.

Charles's English parliament enacted laws known as the Clarendon Code, designed to shore up the position of the re-established Church of England. Charles acquiesced to the Clarendon Code even though he favoured a policy of religious tolerance. The major foreign policy issue of his early reign was the Second Anglo-Dutch War. In 1670, he entered into the Treaty of Dover, an alliance with his cousin King Louis XIV of France. Louis agreed to aid him in the Third Anglo-Dutch War and pay him a pension, and Charles secretly promised to convert to Catholicism at an unspecified future date. Charles attempted to introduce religious freedom for Catholics and Protestant dissenters with his 1672 Royal Declaration of Indulgence, but the English Parliament forced him to withdraw it. In 1679, Titus Oates's revelations of a supposed Popish Plot sparked the Exclusion Crisis when it was revealed that Charles's brother and heir presumptive, James, Duke of York, had become a Roman Catholic. The crisis saw the birth of the pro-exclusion Whig and anti-exclusion Tory parties. Charles sided with the Tories, and after the discovery of the Rye House Plot to murder Charles and James in 1683, some Whig leaders were executed or forced into exile. Charles dissolved the English Parliament in 1681 and ruled alone until his death in 1685. He was allegedly received into the Catholic Church on his deathbed.

Traditionally considered one of the most popular English kings, Charles is known as the Merry Monarch, a reference to the liveliness and hedonism of his court. He acknowledged at least 12 illegitimate children by various mistresses, but left no legitimate children and was succeeded by his brother, James.