Some confusion plotwise!

 Why didn't they ask Evans on ITV in 3 episodes.

I watched it, and liked the production, the clothes, the old cars, the sense of humour but thought the first episode was too slow. 

It is not a Christie novel I have ever read, so I came to it with few expectations. The opening was good. Sharp exchange between young man acting as caddy to an older man on the golf course.  A few minutes in and we have a body falling (or was he pushed?) over the edge of the cliff. But from then on, the pace positively crawls and interest focussed on the character of Lady Derwent though I cannot even recall how she came to be involved at all. But from that point on, she held the piece together.

In the last episode, the plot got rather faint, and how Knocker managed to find them in the dire situation they were in was never explained. Likewise  no one explained how the three of them got out of a locked house that night and then seemed to forget there were two Dobermans guarding the garden.

All the way through the hero was drooling after the blonde but when he discovers she is actually the villainess, he turns about and next thing we see is he marries Lady Derwent. Some confusion plotwise, all in all, but pleasant to watch. Makes me concerned for my own plotting!