All the talk of Mary Hopkin on another thread reminded me that I recently read Tony Visconti’s autobiography. The 2 were married at one time and he produced some of her hits.
If you are interested in the 1970’s music scene, it is well worth a read. David Bowie comes out of it as a decent chap. Mr Bolan on the other hand ...
Tony Visconti: The Autobiography: Bowie, Bolan and the Brooklyn Boy 
