>At http://en.wikibooks.org/wiki/Beekeeping/British_National_%28or_Modified_National%29
I found the opinion that: "Many strains of honey bee bred in the UK are not
comfortable with their brood restricted to a single national brood box. It
is quite common for brood and a half to be used and with prolific strains
such as Carniolan

The National was designed for the smaller nest of the native bee - A.m.m.  They are very comfortable with it.  The problem is the imported strains, particularly the Italian and Carniolan.

I would not describe brood and a half as popular or quite common.  It is an awful system to work in my view - much easier to work double brood if you need extra space.  Single brood is my choice though - so quick and easy to work, and with A.m.m. life is very easy.  Good crops too as we do not get all that honey stored in the brood box.

Incidentally, A.m.m. stores pollen in amongst and under the brood rather than in an arch over the top; this is one of our selection criteria.

Best wishes

Peter 
52°14'44.44"N, 1°50'35"W

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