The Koh i Noor, among the crown Jewels, is the last major diamond in Britain not yet stolen, so it's sent fro safe-keeping to the base at St.Hope. The only link MI9 can go is is the presence at those times of football (soccer) star Ben Lacey, who promotes a campaign to dump 'thieves-attracting' jewelry. The kids fully doubts the brainless star could mastermind anything. In fact his ever-present, slightly brighter brother Reginald is behind it, so his genius nerd accomplice Nigel can make a terrible laser canon. In order to keep the campaign at the school, Stewart is staged as 'football prodigy'.