I found this: http://www.telegraph.co.uk/gardening/main.jhtml?view=DETAILS&grid=A1&xml=/gardening/2008/02/26/garden-beans126.xml
'Climbing French beans are increasing in popularity because they set bumper crops in our hotter, drier summers. Runner beans, on the other hand, are predominantly pollinated by bees, so if it is too cold for the insects to fly, you get little action, while hot summer nights (two consecutive nights of above 16C) prevent runner beans setting and produce sparse crops too'.
I think this explaines why my runner beans were so dismal last summer and why your system of planting later works Clive!
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