See post #4 - there was a power-operated derailer to protect P1.
As in post 4 - In the early 1960s I saw a device not far from the siding exit which I was told was a derailer, something like this: https://goo.gl/images/WiQH9z found in: http://www.clag.org.uk/3rd-4th.html
I am happy for the experts to correct me, as it was a long time ago.
Similarly, from post 23, "All that would be missing would be Q and R Stock.". I will bow to the experts, however I believe this combination might have been covered by the District trains over the North side of the Circle on Sundays, many years ago.
On further information, I have spotted a small detail within an old drawing of the station that shows an elevation of the buffer positions on p1 and the siding. Centre-to-centre of tracks approximately 18 feet.
With a derailer, a wagon could safely be left for rubbish, so I'm happy to concede that wagons may have been left there between trips to store rubbish. But there's no logic to leaving a wagon there after the 3rd August '61 visit, and the available photos from that day don't show that one was left behind to be collected later.
As regards the "missing" Stock, if Engineer_London rereads post #23, he'll see that I only mentioned Platforms 1-4 and the potential for modelling the Stock that would have been seen daily on those platforms. I said nothing about Q and R Stock as they would only have used Platforms 5 & 6 on Sundays. The omission of Q and R Stock was deliberate as 298 was asking for help on the Chiltern Court siding and it seemed to me to be an opportunity to point out the extensive range of Stock that served Platforms 1-4 in the early 1960s. I only threw in the reference to the Bakerloo platforms as a nice to have if there was space.
298 was looking to model a somewhat smaller area that the whole of Baker Street, if I understand his original post correctly. But he will need another MetroVic if he's to replicate the actual loco movements in his proposed micro-layout. How's that for a reason to give Mrs 298 as to why you had no choice but to buy a second MetroVic! More prototypical than using the Pannier tank from your Midnight Metropolitan set.