As the time of Mr Clinton's arrival - 1pm - neared, the numbers soared. He will be signing only 2,000 issues of his book, Waterstone's said, and it is expected there will be hundreds of disappointed fans turned back. A Waterstone's staff member said: "Hillary managed to sign 500 an hour [of her autobiography] - we'll see if he can beat that." Security for Mr Clinton will be tight. The first floor of the building has been blacked out and turned into a secure zone for the duration of the signing, at which Mr Clinton will be flanked by a retinue of secret service agents.