The Lib Dems have launched a new strategy to steal targeted seats from the Tories in their "blue wall" across the south, following the shock win in Chesham and Amersham in June.

       Despite their by-election success, however, Sir Ed Davey's party faces a bigger battle for relevance.

       The Telegraph's Deputy Political Editor Lucy Fisher analyses the key areas where the Lib Dems have been working to gain ground, including the green agenda, tax and spend, and civil liberties.

       Watch the full episode of Westminster Source above.

       For more Westminster Source videos with Lucy Fisher, subscribe to our YouTube channel.