I have tested the three wires in stat and top red wire is common live when programmer activates and next wire down is switched live to boiler when stat clicks on. The bottom wire I assume is neutral?
If I have better look at where wires run I can hopefully confirm what you have stated.
Thanks
I have existing digital programmer and wired room stat to my Baxi combi. I’m looking to replace with hive receiver with wireless stat. From my picture, does it seem possible to just wire to existing position in hallway and not touch boiler?