We hit them with a double barrel I must admit. We hit them both with Douglas Adams and Doctor Who. Between the two of those aspects we managed to get the cast we've got.

I think in the case of James Fox for example, he was just intrigued by the character. We faxed over some of the pages for him to have a look at and he liked the idea of playing Cronotis. He could see why we'd gone for him and when people listen to and watch Shada I think they'll say, 'He is Cronotis, brilliant casting'.

In the case of Susannah Harker, she's a Doctor Who fan. We were discussing this the other night actually. She said when she was growing up all she ever wanted to be was Doctor Who's companion, so she just said yes within five minutes of her agent getting the call. With Sean Biggerstaff, he's a huge huge Douglas Adams fan, and therefore to take part in something which Douglas had written was a dream come true for him. So that was five minutes as well.

Then John Leeson was arguably the best K9 of the two, and we wanted him to do it and he was delighted to do it. Lalla Ward loves coming back and working with Big Finish, we have a great relationship, and she has a very good relationship with Paul McGann as well. And of course, Paul very flatteringly recently has said he really enjoys doing these with us, because a lot of what Paul does is film work, where you go on set and if you get thirty seconds to a minute done in a day you're doing very well.

Here it's an opportunity for him to have a run at acting. He gets the sheet in front of him, he goes for it and he gets to see the results at the end of the day, which is fantastic for him.

And then we've got Andrew Sachs who is a consummate voice artist and was very very enthusiastic about doing something which was connected with Doctor Who which he'd never done before. We had a few problems with Hannah Gordon because she had other commitments but we desperately wanted her, so she only ended up coming in for about three hours. It would have been lovely to have her around for longer, but she was just delighted to do it, because she always wanted to do Doctor Who.