The connector to the Alternator C0226, has no photo, but shows that there are only the two wires identified on the wiring diagram.
Pin1 Colour NY (Brown/yellow) to Gateway ECU
Pin3 cColour LG (Light green) to Engine compartment fuse-box.
These you can see on the wiring diagram going to the Gateway ECU and power, if I read it correctly.
The connector plug could however be on a Ford part of the loom, which means that all bets are off!
Maybe a better image below, otherwise join as a Facebook Two-Sixties Group member and download the whole Wiring Diagram document from the Files section there (and the connectors Electrical Reference manual too).
Rover-75-V8-Wiring-Diagrams-2003-English.pdf
Rover-75-V8-Electrical-Reference-Manual.pdf