Heater valve (overheating)

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I have been working on my cooling system. Everything now connected as it was from the factory. I ran it up today as it was the hottest day so far in Leeds. 31 degrees. Lovely. Ticking over on the drive 20 mins and it started to clime over 95. Checking the coolant pipes in the engine bay the heater pipes were mad hot. Heater valve shut there should be no flow. Heater valve passing? Let it cool down and the heater valve was just held off fully closed. I removed it checked it out when fully shut it didn’t pass but just a crack it passed a lot. It is the adjustment of the cable. The heater knob needs to be set to about 3mm off the dash stop so you are sure the valve is shut. I have set it a bit more. I don’t drive the car in winter so I could clamp or block the pipe. Hope this helps someone.
P.S. If the valve is open it deposits uncooled water straight back into the bottom hose slowly increasing the temperature with the rad not able to cope at tick over (sat in traffic)

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I now understand the cooling system. There is no bypass hose on the water pump to head. The circulation instead is through the auxiliary radiator. Taken from the sandwich plate at the thermostat housings the thermostat has to be above the auxiliary radiator take off to allow continuous flow through the system. From the auxiliary radiator it returns to the bottom of the main radiator having cooled a little, unlike the water through the bypas which is uncooled. In hot weather the heater valve must remain shut to stop uncooled water circulating unless of course you have the heater fan on then it will cool it a little. I have also fitted an electric fan in the n/s wing to draw air through the main radiator when in traffic. I think I wrote about it somewhere else on this forum