Access to the depot

The daylight you can see comes from the hole they use to move stock to and from the line. It's not a very big hole though and the only way to use it is to crane the trains in/out one car at a time.

.....and a picture taken from Spur Road showing the crane.

Daylight can also be seen at the lifting area, as it is covered by a meshwork lid, which is raised and lowered using the four blue winches seen in the first picture (the lid itself is hidden behind the parapet)

The main purpose of the original Armstrong lift was to deliver coal trucks to the W&C's power station (remember that the line was built 17 years before electrification arrived upstairs at Waterloo, and was only connected to the main Southern Railway supply in 1948). On one occasion the lift wasn't secured properly and started to descend under the weight of the trucks before the shunting engine was uncoupled. No 672 ended up at the bottom of the lift shaft and could only be removed one piece at a time .

There are 3 areas in the depot where light comes in. The light most likely seen is probably neither the green or red arrow, but on the inside curve of Spur rd. 
If you look from departures platform, the light you will see is from the opening indicated by both green and red arrows. If you look from arrivals, then part will be from green arrow, but the background light will be from the opening by the inside curve of Spur road. Hope this helps

All still in use

I seem to remember from histories of the W&C I read that there were two lifts,one of which was used to raise coal wagons back upstairs to the power station (they having previously descended to W&C level by the lift on the North side of the main station).
This map dated 1947-64 shows a "Hoist" in more or less the position Roythebus mentions...I hope the link works Ok...
maps.nls.uk/geo/explore/side-by-side/#zoom=19&lat=51.5020&lon=-0.1116&layers=173&right=BingHyb

As previously stated, the area pointed to with the red arrow (in the Google maps image above) has a wire mesh covering.

To the right of the opening is a section of ground that used to be accessible but has now been blocked off - I suspect that someone could still get into this area but they would have to jump over railings intended to keep people out!

However, it was not always like this... in circa 2011 I spent a few months working near to here and was able to walk right up to the metal mesh roof covering the opening where the rolling stock is craned in or out.

In this image Waterloo station is in the distance and of course you can also see the crane - as well as some sidewall metal mesh.



For this next image I walked right up to the concrete wall with the sections of red and peeling white paint - and looked down, towards the tracks - some of which have trains on them. I would have filmed through the square sidewall metal mesh - as can be seen the location from where I was filming was below the metal mesh which prevents direct access from above.



Two trains on sidings below Spur Road plus a non-electrified siding which extends directly below the opening - and has become a rail storage area.

Simon