Thanks Les, I think many may find this guide useful, particularly if they work on multiple computers and are fed up with having to unlock screens every 5 minutes!
I've developed something similar using the Adafruit proximity trinkey. However because company policy prohibits the use of usb storage devices I needed to disable that capability by default in the boot.py file. Storage mode can be re-enabled by inserting the trinkey with the touch pads 1 and 2 conected together (e.g. with a paperclip) - for information the circuitpython boot.py code is below.
""" Disable USB storage boot.py file"""
from digitalio import DigitalInOut, Direction, Pull
# For Proximity Trinkey connect the touch 1 and 2 pins to enable USB
output_pin = DigitalInOut(microcontroller.pin.PA03)
input_pin = DigitalInOut(microcontroller.pin.PA07)
output_pin.direction = Direction.OUTPUT
output_pin.value = False
input_pin.direction = Direction.INPUT
input_pin.pull = Pull.UP
# If the input pin is NOT connected to ground disable USB mass storage
test = input_pin.value