It began as a place of worship circa 604. It's pretty old.
In 1087, under William the Conquerer and as a Catholic Cathedral, a fire destroyed the new construction work. Another fire in 1135 delayed it again.
But like a Phoenix it rose from its ashes and by the 14th Century it had the longest nave and tallest spires in the known world.
After the Protestant Reformation, that began in 1517, the nave aisle became a place of doing business, socialising & horse trading.
In St. Paul's church yard in 1549 radical Protestant preachers incited a mob to destroy many of the cathedral's interior decorations.
In 1561 another fire was hot enough to melt the cathedral's bells and the lead covering the wooden spire "poured down like lava upon the roof", destroying it.
(Rumour had it that a plumber had "confessed on his death bed" that he had "left a pan of coals and other fuel in the tower when he went to dinner." Other records dispute this.)
In 1621, King James I appointed Inigo Jones to restore the building.
Work stopped during the English Civil War between 1642-1651, during which the nave was used as a stable for cavalry horses.
A rumour of the time suggested that Cromwell had considered giving the building to London's returning Jewish community to become a synagogue.
The building was now in great disrepair. King Charles, 1630-85, commissioned Sir. Christoper Wren, to restore the Gothic style of Inigo Jones design of 1630.
Wren saw the building was in such a bad state and felt re-building was the best option.
This was objected to by locals and the clergy alike.
His uncle was bishop of Ely and suggested copying the dome of Ely Cathedral over the exiting cathedral, using scaffolding to support its construction and then dismantling the older cathedral below.
This was to ease the emotional shock that the demolition of a known landmark would cause to locals (Londonners, also known as "non-believers" at the time) and hence any opposition.
Then, in 1666, the Great Fire of London raged, and aided by this timber scaffolding, incinerated the whole construction.
A new building was the only possible outcome after this fire.