What lies, beneath

Spent  practically the whole day with Plumber#8 trying to work out what on Earth is causing the central heating not to make radiators hot in any consistent fashion.  The boiler, pump and pipe bores are all certainly big enough; isolating bits of the system gets them working, which suggests no blockage, but open up the system and the whole thing just doesn't work.

Not helped by the system being creatively/distressingly fudged in places, as it's an evolution of two previous systems.

After much head-scratching and tea we reluctantly conclude the pump doesn't have enough oomph.  Reluctant because it's 'industrial' in size; and cost, and the existing one seems to be 'working' in some sense.

--
Prevaricated slightly whether to drive over to Cambridge tonight or at the crack of dawn tomorrow morning.  Chose tonight and that was a good choice.  Got to Cambridge in two and a quarter hours - the shortest time ever, and at quite a leisurely pace.