It seems that, though BBC TV are rapidly desappearing down the tubes, Radio 4 can still come up with the goods. That said, this is not the best Poirot story in their repatoire, although it's enjoyable all the same. The ending is ludicrous, but surprsing (the fault of Agatha Christie not of the writer) and it doesn't do such a good job of evoking the Middle Eastern setting as the wonderful adaptation of Murder in Mesapotamia did. Also, some of the acting is a little dodgy, most notably John Woodnut, who is miscast as Colonel Carbury.
That said, if you want to be transported to a world of mysterious old monuments and murder in the desert for an hour and a half, you could do much worse. Hugely enjoyable.