Thomas and Captain Wood

The book describes what happens in a city with a ghetto when faced with an existential threat of a magical kind of an interstellar nature. The characters include Thomas the liason man between the ghetto and the city; a sympathetic polise office called Captain Wood and many others from the ghetto and the city. The ghetto dwellers use magic, they say 'Kazoom' and magic comes forth. Their supply of magic rests on magic bars which they touch to supply their magical needs.