Poirot: Agatha Christie's Poirot - Sad Cypress

The solitary extra is an interview with producer Margaret Mitchell. Although laced with relevant facts - the house was a Sue Ryder home, into which they built the lift, etc - it comes across as polished PR. Mitchell's style is positive, upbeat and oh so complimentary towards her actors, every one of which is perfect for the part. Strangely, she doesn't talk of Suchet, like she should, as his Poirot will go down in the annals of Great Performances as exquisite in every detail.

Rupert Penry-Jones was in a play at the time and had shaved his head. They wanted him for the part of Roddy, the faintly wet fiance, so much that at considerable expense a wig was made for him. It took three weeks. That, believe it or not, is the most interesting anecdote Mitchell comes up with.

Interviews as sale pitches are not the stuff of DVDs. Viewers are too sophisticated for that. They may crave gossip, but prefer Making Of behind-the-scenes revelations about the tricks of the trade, cock ups and what it feels like to be there, having done that.