WI Doctor Who dies

Something I ever wondered, what if one of the actors playing doctor who (any of them) died during the show before his regeneration? Would the studio hire a doublé or something to replace him? Would a offscreen regeneration happen (This is the new doctor, the other regenerated when no one was looking)?
 
They effectively had to do this when Colin Baker refused to come back to film a regeneration scene. Instead the Sixth Doctor was played by Sylvester McCoy in a blond wig.

Cheers,
Nigel.
 
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