Original: However, by October 2007 the date for the first train entering service had slipped to January 2009, and the first train entered service on 21 July 2009, leaving the depot at 23:00 and forming train 277 leaving Seven Sisters at 23:55 to Brixton.
Simplified: However, by October 2007 the date for the first train entering service had slipped to January 2009. The first train entered service on 21 July 2009, leaving the depot at 23:00 and forming train 277 leaving Seven Sisters at 23:55 to Brixton.