London's Great Fire of 1666, following a devastating outbreak of plague in the city which killed a fifth of its population, spurred the commission of Christopher Wren to rebuild St. Paul's Cathedral, which occurred over the course of 35 years. Robert Hooke, who first articulated that a thin arch was comparable to an inverted hanging chain, may have advised Wren on how to achieve the crossing dome. Wren may also have been informed of the structural problems of the dome of St. Peter's Basilica by John Evelyn, who had examined it, and did not finalize his design for a dome three-quarters its size until shortly before its construction started in 1705.