Shelly 1L/Dimmer in 3 Way Switch UK

I am looking to install a Shelly 1L or a Dimmer with no neutral into a 3 way switch.

I’ve searched the internet and can’t seem to find clear diagrams on how to do this if an intermediate switch is involved.

This diagram is my current setup:

Any any advice on where the shelly would go in this setup?

This is the way.