pert:
Unfortunately there is a bug with the avrdude 6.3.0-arduino12 included with the Arduino AVR Boards 1.6.20x beta package that causes this error when you try to use an Arduino as ISP:
Arduino as ISP programmer can't be used with avrdude 6.3.0-arduino12 · Issue #11 · arduino/avrdude-build-script · GitHub
The solution is to downgrade to Arduino AVR Boards 1.6.21:
- Tools > Board > Boards Manager
- Wait for download to finish.
- Click on "Arduino AVR Boards".
- From the dropdown version menu, select "1.6.21".
- Click "Install".
- Wait for installation to finish.
- Click "Close".
You absolute legend! I've spent about three evenings getting nowhere with this, I have just done as you said and bingo, away it goes.
Thank you to everyone who replied. Your kind time and attention is much appreciated.