"We must never include a product or service in sound or vision in return for cash, services or any consideration in kind," says the BBC's website. "This is product placement."
But there are other ways to ensure that editorial content is profitable, especially important at a time of recession and managerial hotel expenses.
Cue the return of Doctor Who. According to Private Eye magazine, BBC Worldwide, the corporation's commercial wing, suggested that there might be extra, vitally needed funding for the show in return for new merchandising opportunities.
In the year of the show's relaunch Worldwide made £15 million from Dalek toys. So, sure enough, the series returned last month - with five colourful, newly designed models of Dalek. Get them all, kids!