Hot to get a neutral wire to a UK light switch [Theoretical]

For the majority of UK homes (The older ones at least) our lighting switches are wired up with a system called 'loop in ceiling' where all the light fittings in the ceiling (ceiling roses) are wired in a loop, with a switched live being taken from the rose to the switch. This can potentially save cable and simplify installation, but causes issues when you want to install Home Automation type switches such as the Sonoff T1 that need a Neutral to be able to power themselves.

This is something I've been mulling over for a while, and someone has asked for more details. So here it is, a quick and dirty blog post.

Below shows a standard wiring layout for a single switch and bulb, as you can see there's no neutral in the switch, only live in and switched live out.

The Problem (Click to expand)

So, can we get a neutral to the switch without tearing the walls apart? Kind of!

I am not an electrician. This may not meet building or safety regulations. This is untested! Do so at your own risk! Electrical work should be carried out by a qualified electrician! ETC