Luxury properties in the Kensington and Chelsea district of London, U.K. Bloomberg | Bloomberg | Getty Images This report is from this week's CNBC's UK Exchange newsletter. Like what you see? You can subscribe here. The dispatch Jockeying for position in the as-yet-unlaunched contest to lead Britain's governing Labour Party, Wes Streeting, the former health secretary, has promised a wealth tax if elected leader. "We need a wealth tax that works," he told the BBC last week.