Thank You @CrossRoads. I added a switch made from 2-BSS84 P-MOS controlled by the SD Card CS line to isolate the SD Card.
The real joy came when I defined the SCK line as an output with an initial state of LOW in the set-up and it started to function as expected. See #3 of this post: SPI Communication Problem on Pro Mini / 5V @ 16MHz - Networking, Protocols, and Devices - Arduino Forum
Any body here know of a list of similar mis-behaving SPI devices?
SDCardDataSwitch.pdf (4.8 KB)