the cadences are the same.

TV A-list Doctor Who fan Ian Levine has created a version of lost Douglas Adams story Shada, filling in the gaps left in the recording (which was finished due to industrial action) with animation, voiced by Lalla Ward and various mimics. Starburst Magazine website offers a review:

"First, I must state that the timbre of Paul Jones’ voice is different to that of Tom Baker’s, and so there’s never any question of the fact that you’re listening to a different man. Having said that, there were occasions, particularly towards the end of the story (during sequences in which the ‘original Tom’ hadn’t been on screen for a fair amount of time), when it was very easy to forget that you weren’t listening to (or watching, even) the authentic fourth Doctor after all. The timbre of the voice might be different, but the cadences are the same. There are moments that are scarily familiar, even. The performance is set to fourth Doctor ‘maxed up’ a little, but if anything, that’s probably because attempting a subtle Tom Baker would have been incredibly difficult, and as the story progresses, Jones is comfortable enough to tone it down."

2Entertain apparently have their own idea on how to prepare the story for dvd release, but if they fall through this sounds like it could be a useful back-up [via].