Possible Clues:

• A thousand million
• Huge number
• One thousand million
• 1,000,000,000
• Large sum in gold university's transferred to Italy
• How William gets charged a huge amount
• Put one more on the bottom of the account to make it almost countless
• William backed up no-one a lot
• So very many must be paid with one on the end
• The enormous amount of account gets a further one on the end