[MR2] Removal of Speedo cable drive

[DAVIES, BARRY S (BARRY)]

I'm (slowly!) getting my 20v conversion done. One of the things that
needs to be addressed is the C56 tranny has an electronic speed sensor,
and the C52 has the mechanical one.
I have a spare C52 so plan on using the speedo drive from that. But,
daft as it seems, I can't remove the drive.
There is a single bolt, which holds a tab in place. Removing this
doesn't seem to get me anywhere. Studying the BGB shows a spring clip
somewhere, but I can't see it. Instructions in the BGB for disassembling
the tranny just say: Step n: "remove speedo drive"
Anyone got any insights? 
Thanks
Barry