Portrait of an eccentric family in London; father Sykes is rebuilding the Old Bailey in the sitting room, son Miller is teaching weighing machines to sing, etc. Completely rooted in the culture of 1960s England, it might not be relevant at all today, but it is quite amusing to those who give it a chance.
Most of the supporting cast play dual roles, but are only credited for one role in the cast. I have listed the actors in credits order, with their main role first and minor uncredited role second. Hopefully it isn't too confusing.
Note: The poster isn't the original film poster, which could not be located, but one made for Monorail Film Club's 2010 showing. I think it suits the film quite well.
Thanks to Philly for his help, as always!