In the Dumas classic *The Vicomte de Bragelonne,*he writes about Monck's siege of London:
Monk (sic) pronounced this declaration, supported by fifty thousand swords, to which, that same evening, were united, with shouts of delirious joy, the five thousand inhabitants of the good city of London. At length, at the moment when the people, after their triumphs and festive repasts in the open streets, were looking about for a master, it was affirmed that a vessel had left the Hague, bearing King Charles II. and his fortunes.
From Chapter 31. Monk reveals Himself.
So was the population only 5000 or was this the City of London and not the whole metropolis?
The population of the London metropolis was about 400,000 people at the time of the Restoration, and was likely somewhat higher (Wrigley, "A Simple Model of London's Importance in Changing English Society and Economy 1650-1750" Past & Present (1967) p. 44). It's difficult to say what the population was inside the walls, but 5,000 is nowhere close. In 1548, with a less compact population, the number of people living around London was about 60,000 (Brigden, New Worlds, Lost Worlds, p. 295). By 1660, the population living just within the ancient walls probably matched or exceeded that number (London Inhabitants Within the Walls, 1695).