Task: Question Answering
Input (English): Passage: Tuesday, 4 September was the day of greatest destruction. The Duke of York's command post at Temple Bar, where Strand meets Fleet Street, was supposed to stop the fire's westward advance towards the Palace of Whitehall. He hoped that the River Fleet would form a natural firebreak, making a stand with his firemen from the Fleet Bridge and down to the Thames. However, early on Tuesday morning, the flames jumped over the Fleet and outflanked them, driven by the unabated easterly gale, forcing them to run for it. There was consternation at the palace as the fire continued implacably westward; "Oh, the confusion there was then at that court!" wrote Evelyn.
Working to a plan at last, James's firefighters had also created a large firebreak to the north of the conflagration. It contained the fire until late afternoon, when the flames leapt across and began to destroy the wide affluent luxury shopping street of Cheapside.
Everybody had thought St. Paul's Cathedral a safe refuge, with its thick stone walls and natural firebreak in the form of a wide empty surrounding plaza. It had been crammed full of rescued goods and its crypt filled with the tightly packed stocks of the printers and booksellers in adjoining Paternoster Row. However, the building was covered in wooden scaffolding, undergoing piecemeal restoration by Christopher Wren, who was relatively unknown then. The scaffolding caught fire on Tuesday night.
Leaving school, young William Taswell stood on Westminster Stairs a mile away and watched as the flames crept round the cathedral and the burning scaffolding ignited the timbered roof beams. Within half an hour, the lead roof was melting, and the books and papers in the crypt caught with a roar. "The stones of Paul's flew like grenados," reported Evelyn in his diary, "the melting lead running down the streets in a stream, and the very pavements glowing with fiery redness, so as no horse, nor man, was able to tread on them." The cathedral was quickly a ruin.
In St.Paul's, falling heavy masonry broke through into its crypt, where booksellers had stored huge stocks of books, and all were burned.
During the day, the flames began to move eastward from the neighbourhood of Pudding Lane, straight against the prevailing east wind and towards Pepys's home on Seething Lane and the Tower of London with its gunpowder stores. The garrison at the Tower took matters into their own hands after waiting all day for requested help from James's official firemen who were busy in the west. They created firebreaks by blowing up houses on a large scale in the vicinity, halting the advance of the fire. In a letter to William Coventry, Pepys wrote that he "saw how horribly the sky looks, all on a fire in the night, was enough to put us out of our wits; and, indeed, it was extremely dreadful, for it looks just as if it was at us, and the whole heaven on fire.". 
Question: What is the last name of the person who was restoring the building that was thought to be a safe refuge from the fire?
Output (English): Wren.