Later we went for a short walk and saw two more sundogs, both of which seemed to have formed in the contrails of passing planes.
All these pictures were deliberately underexposed as the sundogs themselves were so bright that all detail would otherwise have been lost.
Sundogs are also known as parhelia or mock suns. Like halos, they are caused by sunshine on ice crystals in clouds and are seen quite frequently.
You can read more about sundogs, halos and other similar phenomena at the following websites:
(This site also has software for creating your own haloes)