Hi @orangutan
In switch 2 how many cables did you have originally? If only 3 cables then grey and black in L1 and L2 are original but where 2 red cables comes from/into? Or you had 5 cables in switch 2 originally?
There were 5 in Switch 2 originally and the two red ones were moved to connect to the Sonoff device instead.
Installed Sonoff ZBminil today and worked. Very easy to follow thanks to the image . Thanks for sharing this image.
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Another +1 for this diagram, thanks it saved me a ton of time.
For my hallway / landing lights this was perfect, as the hallway was in the downstairs dual switch so fitted one zbminil2 in there, and the landing lights had the live in the upstairs single switch, so one in there.
In my kitchen / diner it’s a bit more difficult - not with the wiring, with the fitting of it.
We have 2 switches, one single one for dining room lights, and then a dual switch for kitchen and dining lights… problem is BOTH sets of live wires are in the dual switch 
the remote (single) switch is just that. Meaning I have to try and fit two zbminil2’s into a single socket. Even with a few spacers it’s proving very very tricky.
I’ve done diagrams and wracked my brain but can’t work out any obvious way to put the zbminil2 in the remote switch - don’t think it can be done. Ah well, back to squeezing cables lol
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Have you thought about wiring the ZBMINIL2 up in the ceiling rose or void end instead?
@esquirefahad14 I have the same setup as yours and I struggled to understand how to wire it up at first. However, the first post does describe your setup also, it just isn’t that obvious at first glance. I had to sketch out my own switch in order to understand, and we have the same setup (although your colours are slightly different to mine).
The top of the image is what I have and the bottom is what I think I want.
I need to confirm what is connected to the light on the other end but that black wire should be the switched live which powers the bulb, then I would expect to see another wire at the bulb which is the return (neutral) back to my consumer unit.
So to wire the sonoff:
From the two core cable:
L in = red
L out = black
From the three core cable:
S1 = COM (common, from one switch)
S2 = COM (common, from other switch)
In my case, I will disconnect the COM from the switch and connect it to S1 on the Sonoff. Then I will get a new piece of wire and connect S2 to the COM I just disconnected. You should not need to touch the other switch (but would be good to check the red still goes to COM).
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For those trying to understand the old versus new (UK) colour coding the diagrams at Flameport.com might be useful (although as the above post shows there is obviously some flexibility in how rigidly these are applied).
Two way switched lighting circuits #1
But they do fill in a bit of a gap in showing how the slave switch (3-wires only) differs to the master switch (5-wires).
Old (pre-2005)
New (post-2005)
In essence when using the ZBMINIL2 it is doing the actual switching circuit via the permanent live and switched live (uppermost 2-core & earth cable depicted exiting the top of the pattress) and the remaining wiring is re-purposed to have the manual switches trigger the relay.
But like many I found the Sonoff diagram a little unclear and the OP’s diagram has helped enormously.
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