What is going to be done to properly maintain the tracks between Clapham Junction and Waterloo?

There have been several days where speed restrictions have had to be put in place recently - doubling the journey time from Wimbledon to Waterloo.

While this is bad enough, given that these trains depend on a flow of air from open windows for any form of ventilation (as there is still no a/c on most of the trains) this makes for an abysmal journey.