Change default behaviour of Virtual Keyboard Shift key

[MartinSmith2770]

The default shift behaviour for the Shift key on the Virtual keyboard is:
Single Press -> Caps lock for the first character
Double press -> Permanent caps lock

I would like to change the behaviour to just Single press -> Permanent caps.

I think I have to provide a custom InputMethod but I'm not sure the correct mechanism.

Could anyone provide any assistance, please?