I wouldn't put this down to onion white root rot. That gets the crop while it is growing. I think the wet late summer was mostly to blame. I wouldn't hurry the ripening of onions if they are to store well. Their going dormant is not encouraged by drying with fans or breaking their roots, and especially not by bending their tops over while they are stlll green — this practice has long been discredited. In fact they will store best if they are left to die down of their own devices. Last year they ripened off very late, and it might be that the time you harvested them in previous years was perhaps just a little too early this last season, which was a late one.

mine aren't storing too well, about 50% have sprouted, which is most unusual. (cupboard under the stairs is where they are usually stored)

Dear Retropants, sounds as if they are getting a little warmer than normal.

could be as it has not been a very cold winter this year, they are normally fine under there!

Hmmmm, very interesting reading and got me worried about my first-ever crop of onion and garlic sets planted just a week ago. I did wonder about winter crops and whilst this is not the coldest part of the UK it isn't the green-and-pleasant land for any fanciful reasons of green fields and clear blue skies.

It rains here like the Amazon, mostly sideways.

The onion and garlic are in well-drained beds. "Well drained" now after mixing sand and rotted compost into the clay-like stony soil. Should I cover the onion/garlic beds ? Fleece maybe ?

I wouldn't worry, Richard. I always grow overwintering onions and garlic and they have withstood temperatures down to minus 11 here. I do cover them with wire netting to stop the birds from pulling them up, but certainly no weather protection.

this sounds to me more like the effects of downey mildew. the spores infect the leaves then travel downwards into the neck making them soft & rotten giving off that terrible smell. most white rot i have seen turns the leaves yellow because the roots have been eaten away & the basal plate contains the tell tale white mould with the smell. necks seem to remain ok.