A swarm of bees !!!

We have had a lot of rain over the past few days; the garden has exploded with growth and I shook the delphiniums and lupin spikes (gently) so that the weight of the water wouldn't bend them over and break them.
Today we witnessed something that I have only ever seen twice before in my life - a bee swarm.  We were outside working when I heard the noise, and there, coming across the yard about 20 feet up was a dark cloud of thousands of bees, in a sort of circling, moving mass.  It was an astonishing sight.  Our old dog, oblivious, was flat out asleep in the sun.  I ran through the house to call him indoors, lest they should descend upon him.  He came to the whistle - I quickly grabbed my camera and cautiously went back out.  The swarm was moving across our garden and I watched as it descended onto the building roof.   The whole mass seemed to contract as they settled on the woodwork and in a few minutes all had gone quiet.
I did a bit of research about them.  They are probably on a 'stopover' while the scouts are sent out looking for a permanent home.