Stuck Bonnet Release

My '65 Mark 2 refuses to release the bonnet. The actuating cable freely pulls the releasing mechanism to the open position, but nothing happens. The catch has been well lubricated, and I am now contemplating entering the latch area through the access plate opening at the bottom of the radiator and using a BFH on an extension to drive the latching device out. That’s really more than I want to do. Is there another approach?

if you can see the latch operating have to tried pulling on the bonnet using the jaguar motif

And a further suggestion to try: Have someone push down on the bonnet while you attempt to pull on the cable handle. This may relieve strain on the latch and allow it to release.