Proper pouring with rain this morning, and temperature is, dare I say it, a positively autumnal 13° C.
Luckily I had only yesterday found that one of the water butts hadn't been filling, so stripped the pipes out and found a stone blocking the diverter to the outflow pipe - how a stone that size got into the roof gutter to be washed down in the first place is another mystery. Anyway, I suspect that one is full again this morning.