Complex sentence: S7 Stock began operating a full passenger service from Hammersmith to Barking on 9 December 2012, with all Hammersmith & City and Circle line trains formed of S7 Stock by 2015.
Split into simpler sentences: S7 Stock began operating a full service from Hammersmith to Barking on 9 December 2012. It is planned that all Hammersmith & City and Circle line trains will be formed of S7 Stock by 2015.