In message , at 21:11:51 on Thu, 10
Jan 2013, " remarked:
36. The eastern extension of the Jubilee line is the only Underground
line
to feature glass screens to deter "jumpers".

No, it's to do with ventilation.

How so?

By keeping the track alongside the platform part of the same reasonably
airtight tunnel as the rest of the running tracks, avoiding air
'escaping' into the platforms and beyond.
--
Roland Perry