The Mousetrap Understudies through the ages?

Hello everyone, 

So I am a saddo who loves compiling cast histories and I thought I would really challenge myself and try to backtrack through all the casts of the Mousetrap (London production).

So far I have a complete, up to date principle list, but I am really pushing it and wanting to try and gather understudy information. 

So far I have...

1985/1986
Stephen Marzella (Understudy Giles Ralston, Christopher Wren & Sgt Trotter)
Alex Spencer (Understudy Mollie Ralston & Miss Casewell)
Nancy Seabrook (Understudy Mrs Boyle)
Alex Blythe (Understudy Paravacincini & Major Metcalfe)

2004/2005
Emma Tapley (Understudy Mollie Ralston & Miss Casewell)
Henry Douthwaite (Understudy Giles Ralston & Sgt. Trotter)
Terry Grant (Understudy Christopher Wren)
Virginia Courtney (Understudy Mrs Boyle)
Livy Armstrong (Understudy Paravicini & Major Metcalfe)

2006/2007
Meg Dixon (Understudy Mollie Ralston & Miss Casewell)
Sam Emery (Understudy Giles Ralston & Sgt. Trotter)
Will Rowbotham (Understudy Christopher Wren)
Virginia Courtney (Understudy Mrs Boyle)
Martin Bendel (Understudy Paravicini & Major Metcalfe)

2016/2017
Harriet Leitch (Understudy Mollie Ralston & Miss Casewell)
Ben Riddle & Edmund Sage-Green (Understudy Giles Ralston & Sgt. Trotter) 
Anton Tweedle (Understudy Christopher Wren)
Mandi Martin (Understudy Mrs Boyle)
Jason Hall & Clive Marlowe (Understudy Paravicini & Major Metcalfe)

I also know that Nancy Seabrook acted as Understudy to Mrs Boyle from 1978 - 1992

Anyone know of any other understudy lists?

Thanks