Steam Brake Questions

Interestingly Bradley has the incident down as occurring in 1890, but the incident is so obviously the same from his description and the report that it must have been this 1900 incident. He does positively identify the locomotive as Jubilee No. 556.

I suspect that the Westinghouse fitted Jubilees used the steam brake cylinder for the air brake, much in the mould of the Adams O2s when they were converted for service on the IoW. The vacuum would then have controlled the air brake cylinder much like a steam brake, as per the system shown in Fig. 86 of the black book. It's quite a neat system, and as long as your air pump is working air is a better medium for brake actuation than steam.

The system on 35028 is based around a diesel-era air-to-vacuum proportional control valve, where the air train pipe controls the vacuum train pipe with the assumption that all braking is controlled through the air brake valve, so not like the image below at all.

 

In the 1892 Appendix there were no instructions concerning the working of the Westinghouse Brake, but there was an instruction that the Vacuum Brake should not be used to slow down or stop at a station, except in emergency. and from @LMS2968 it appears that the South Western weren't unique in this.
I have a note that the loco involved was 556, another Jubilee 0-4-2. Until 1901, when 2 T9s were dual fitted, 6 Jubilees were the South Western's total of dual fitted locos.
Pat