William Broughton Carr was the 'inventor' of this hive which these days is characterised by the often white painted, taper-sided (telescopic) lifts, which most people in the UK will recognise as a beehive.
The WBC is the only double walled hive now in general use. It has changed designs over the years and before the introduction of the telescopic design we now recognise, they were straight sided with plinths around the bottom that overlapped the top of the lift below to allow water to run off. The reason for the lifts is to cover the inner boxes that are made of much thinner timber and to increase insulation.
Before standardisation, virtually all manufacturers had their own sizes that created a lot of problems, especially if buying hives secondhand. This is no longer the case and hives from all major manufacturers should be compatible.
It is often felt that the double walled concept was warmer for the bees in winter than single walled hives, but in my area I have not seen any noticeable difference. I suspect colonies in WBCs may take a little longer to get going in the spring, due to the greater insulation. I'm sure there is an advantage in more exposed areas.
The maintenance needs to be good, otherwise damp will get in the cavity during the winter and be bad for the bees.
For a number of reasons WBCs are discredited, but in 50 years of beekeeping I have been involved in using many of them. I think they are as good as any hive for the ordinary beekeeper who wants to keep a couple of hives at home. The problem comes when you have a number of hives, because you have a lot more equipment to store and maintain and colony inspections take longer. I haven't used WBCs myself for a long time, but regularly handle bees belonging to other beekeepers and demonstrate when invited to at other BKAs. If they are well looked after the bees won't mind what they are in.
They are expensive compared to Nationals, but the amateur beekeeper may not be concerned about cost.
The frames used are B.S. and in the past many beekeepers ran both WBC and Nationals as the frames are interchangeable. The WBC brood box takes 10 frames and is said by some to be too small for what they call the "modern" bee, but with non-prolific queens I have found you can keep bees in them throughout the year without the threat of starvation. On many occasions I have taken large crops of honey from them.
Beware of secondhand WBCs as there are often bodged repairs and home made brood boxes and supers - very often these aren't the correct size and badly made.