Disconnect at top.
\turn mower on side.
Remove roller (undo 10mm nut and pull bar out (catch the washer and spacer!)
Remove the roller housing bracket on the right side (2 screws and a metal plate. I always leave the other side with the screw way up inside.)
Remove the Throw Plate (big plastic guard) with 4 screws (2 either side)
You will now see the other end of the cable attached to the jockey arm.
Disconnect from jockey arm (and unhook from compensating pulley) and thread out.
Fit replacement cable back in reverse and adjust as necessary.