Pretty sure that's cable operated.
Had a similar problem with my '76 once.
Pushed it out onto the road, where there is a slight downhill. Put car in first, started it on the starter, in gear (don't put power on for long, starters don't like it!). Drove down the road with clutch pedal depressed, with a few revs on. A couple of hard brake applications broke the clutch free. Went for a long drive
