To be fair, it was one train in and one train out, and upon arrival it did wait for several passenger movements before entering the station. So from a congestion point of view the train itself didn't really do much damage. As to whether 21-24 are still officially available for passenger use (to ease congestion) I couldn't tell you, however I did ask a chap there this question and he said they can't, for one they haven't enough staff available to dispatch, and something else about the gateline, I didn't quite catch it.
I do wonder how much of the media reports will focus on the things and how much will focus on the infrastructure and train problems. I've come across at lest three train failures in addition to everything else..
If any of the press were using the network to get to Waterloo, they might even be caught up in it. Even if not they can see the display boards and read Twitter.
Currently the lines between Wimbledon and Clapham Junction are open with delays of up to 20 minutes and that is expected to continue until 22.00. The signaling issue at Portsmouth has also been resolved and the lines are all open. There are still delays of 60 minutes but despite delays of up to three times the length of that at Wimbledon, the distortion at Portsmouth is expected to be resolved by 15.30. I guess with less trains running they can resolve the disruption more easily.
So a rather unfortunate day to hold the launch but had they cancelled it, they might have looked even worse so they just have to make the best of it.
Despite falling newspaper sales, companies like SWR obviously still feel there is merit in doing promotional activities aimed at the media.