Diode used in Roberts RD50 & RD60 mains/battery switching circuit

[Old Sparky]

I've since found that, after a few seconds on Battery operation the radio 'dies'. This is due to one faulty Duracell 'UltraPower' 'D' cell, which must have delveloped high internal resistance, as it reads very low on the Battery Test Function of an analogue meter.