Musical theatre stars Jenna Russell, Daniel Evans and Janie Dee remember working with their hero, and the unique demands and rewards of his songs Sam Mendes: 'He was passionate, utterly open, sharp as a knife' So much of his work is about love. People talk about it being cold but as a teenage girl all I could feel from it was warmth. The songs are ridiculously rich. I'd play the original cast recording of Company aga…