help me find C wire on williamson boiler and where should I connect it

I have Williamson boiler GWA 140,000 BTU. I have 2 zones in my house for heating. On one zone I want to install smart thermostat so, I need C wire. The old thermostat for this zone had 2 wires: red and white. The other zone’s thermostat has 4 or 5 wires.

I am attaching the photos of boiler’s wiring and one and off switch. Also can you tell if I am connecting c wire for only one zone then, should I do it at zone valve or at the thermostat?

Image 1, shows the C wire I found and the manual says it should be to black wire to left on TSTAT wiring in third image

Image 2,Just the boiler and all the wiring

Image 3,TSTAT for red, green, white etc wires. BUT ON THIS BOILER IT DOESN’T FOLLOW THAT

Image 4,This is the on and off switch. The wires from the zones valves are connected here. The Transformer here has a blue wire. Does it mean the thermostat with 4 or 5 wire cable running has C wire?

Image 5, This is low water cutoff and the C wire in Image 1 is connected to white wire which connects to this low water water cutoff sensor.

Image 6, Another view of on and off switch. The black tape is where zone valve wiring is connected