You may know Derek as the voice of multiple Look & Read series, notably Through the Dragon's Eye.
Skip a minute to get a montage of the breadth of Derek's singing through the Look & Read series:
This is Derek with Marty Feldman:
And now Derek's on a bike!
Here he is facing off Alf Garnett in Til Death Do Us Part. The 1970's were very depressing, even if Alf was supposed to be an ironic pastiche of a typical boorish racist: