The only review I have seen of Murder in Samarkand on Radio 4 is from Chris Maume in The Independent. While he says some great things about the play:
The terrific Murder in Samarkand
David Hare’s superbly brisk, no-nonsense script
[David Tennant]
put in a fantastic performance
I really don’t agree with his balancing criticisms of David Tennant – I think David pulled off the huge emotional range required brilliantly.