My thanks to Terrywookfit & giblets for their advice. Seems obvious now that just restricting the flow would cause the heat-exchanger in the Aga to boil or worse. Checking on the Aga web-site it may be possible to have the Aga modified to remove the water heating element. This could potentially...
The house we have moved into has an Aga. This has a water outlet used as a secondary water heat source - secondary to the main boiler. It also feeds a small radiator. This is a conventional, open vented, gravity system. The large bore piping used must be a major source of heat loss.
Is it...