So, I've been doing a massive rewatch of Classic Who. Started with Trougton, which I had seen very little of previously (Including the Reconstructions for the missing episodes), watched all the way through Pertwee, and just finished Key to Time last night. So, I was wondering, why exactly did they Regenerate Romana and switch over to Lalla Ward? I love both actresses in the role, and I love the explanation for the Regeneration in Gallifrey Adventures Audio Series, so I'm glad we got both of them. Just wondering, behind the scenes, why the change? Did Mary Tamm want to leave, or her contract ran out and re-upping her would've been too expensive or what exactly went on? Did they know when filming The Armageddon Factor that they were going to use the Astra Actress to continue the role of Romana, or was that a las minute afterthought when they had to replace Mary Tamm?
Mary Tamm wanted to leave, because she felt the character had not developed as it had been suggested she would, instead becoming another screamer. Tamm herself suggested the possibility of Lalla Ward taking over the role. The producers had originally hoped to have Tamm return for a regeneration scene in "Destiny of the Daleks," but she was heavily pregnant and unable to do so.
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.
I wonder (since the Tom/Mary Big Finish episodes are set between The Armageddon Factor and Destiny of the Daleks) if, taking Mary's failing health into account, they wrote/recorded a proper final scene/regeneration for Mary (in the last one she did before dying, yet to be released) to become Lalla. It would be a fitting - and poignant - thing to include in the 50th Anniversary festivities.
"Hey Mary, since you're clearly on the way out and all, how about doing a proper regeneration before it's too late? " I seriously doubt it.