Some good news. One of my friends just ran the Stevenson protocol twice. The first time he called me and said 'it doesn't work' - but then he discovered there was an internal short circuit - so I got a very happy call 15 minutes later saying 'yes it works'. Just 200mV and the current too low to measure with a low-impedance meter.
Then he dismantled the cell, stripped off the plating, re-plated the working electrode and it worked again. He has no hydrogen to hand, so for now it's sitting in a jar of Argon to slow down the corrosion - and its still working.