Re: The Changing of Romanas
Mary Tamm's contract ran out, and she didn't want to stay (plus she'd found out she was pregnant), but Graham Williams kept hoping he could persuade her to change her mind. Casting Lalla Ward was suggested by various people who'd seen how well she and Tom (increasingly cantakerous at this point) got on (including Mary Tamm), and hoped it would come across onscreen and help make him more cooperative on set.
"Some days are better than others. They say that where I come from."
"Loudly, I imagine, on the day you left."
(Blake's 7 - Rumours of Death)