TOP OF THE LAKE, BBC2, 9pm
MY God, where to begin? I think I’ll need to begin at the end.

The final scenes in tonight’s episode are ludicrous. Everything goes utterly wild, and I laughed nervously as I watched. Yes, I was nervous: are the writers playing a trick on us? They can’t expect us to take this seriously? Maybe I’ve got this wrong and it’s actually a comedy? Or maybe I’m hallucinating? And how am I supposed to preview this episode without using the letters “WTF”?

But even though it was utterly over the top, verging on silly, it was mesmerising. I could not look away. I even skipped back and watched it again.

Who cares what else happened? OK, I’ll try to remember: there’s a brilliantly awkward scene in a posh restaurant where Julia and Pyke think they’ve discovered some dirty truths about Puss, so he taps his wine glass and makes a public speech to humiliate them.

PRINCESS DIANA’S ‘WICKED’ STEPMOTHER, C4, 9pm
THERE was such a stramash last week about Channel 4’s decision to broadcast footage from supposedly private tapes where Diana spoke bluntly about Prince Charles’s courtship technique. I saw a preview copy and was left quite deflated and ever so slightly bored. The problem is that Diana just wasn’t that interesting. The effect she had on the Royal Family and British society was engrossing, but the lady herself? Nah. So I’m glad she’s not the focus of tonight’s documentary as Channel 4 gladly wade back into controversy by profiling Diana’s stepmother and their fractious relationship.

Raine Spencer, daughter of the pink-tinted romance writer, Barbara Cartland, married Diana’s father in 1976 when the Spencer siblings were still young. They didn’t take to their new mother and used to sing “Raine, Raine, go away”. But you have to admire “acid Raine”. The social climbing Countess had a bit of spark to her that the anaemic aristocracy obviously lacked.