In the olden days, when I was young and Fortnum & Mason’s had that soda fountain on the ground floor, I once sat next to a man who told me he’d been married to Joanna Lumley. I don’t think it was a pick-up line (for the record: talking about beautiful, brainy ex-wives is not seductive); he was simply recalling better days.

Over the years, I’ve missed that soda fountain and come to adore Joanna Lumley. Listening to her last week on Desert Island Discs was sheer heaven: the gorgeous voice, the perfect choice of music?Beethoven and Elvis?and her brilliant common sense. She endeared herself to me even more by her attitude towards life’s little negatives. An unflattering photograph? Tear it up. A critical review? Throw it away. Don’t let it bring you down.

My policy entirely (the photograph at the top of the page is beyond my reach), and I’ve gone through life editing out the bad marks, the sharp rebuke, the gloomy appraisal. When I received a report card, age seven, stating ‘Carla accepts criticism well’, I quit school. I was required by law to return, but my heart was no longer in it.

Editing life so that it feels better doesn’t always work. Putting on make-up in front of a mirror lit with 40-watt bulbs, then seeing yourself in the Peter Jones dressing room can deprive you of your will to live. On a pastoral note: when the countryside had patches of vibrant yellow, you could pretend that it was mustard and romantic and French. Now that it is a violent yellow sea, all pretence is over.

But there is a difference between tossing out the picture that shows the subcutaneous fat under your chin and telling yourself you have the jaw line of Audrey Hepburn. It is called deceit. On an agricultural note: that is exactly what we are doing. We’re telling ourselves that biofuels are good, that they are sweet to the planet and liberate us from the yoke of Middle Eastern oil. The truth is: biofuels may be the nail in the planet’s coffin.

I don’t like saying it. I’m a farmer and wheat has just reached a 10-year high. Optimism doesn’t grow naturally on the Suffolk prairies, but it is seeding down as grain prices rise, and global stockpiles hit a 25-year low. Why? Because of demand for ethanol, the alcohol made from maize and wheat that can fill up our petrol tank (ok, and the farm bank account).

So that we can feel virtuous as we drive through the yellow countryside, virgin habitat is being ploughed up all over the globe. The UN predicts that the natural rain forest of Indonesia will have disappeared in 15 years, because of the planting of palm oil to turn into biodiesel for the European market?palm-oil biodiesel that causes 10 times as much climate change as ordinary diesel. It’s about more than orangutans. The fuel planters are bulldozing South America, Asia and Africa, literally ploughing up the planet.

My husband used to search my family tree: ‘Your folks have been in America for 300 years and they don’t even have a chain of gas stations?’ I saw biofuels as the chance to compensate for my ancestral lack of verve. Now I suspect that filling up Volvos with biofuel will do more harm than good and I wonder how we can press the ‘pause’ button while we rethink this.

On my personal Desert Island list was always the Supremes singing Stop! In the Name of Love, apt now because we desperately need a freeze on biofuels. But the song I can’t get out of my head is Neil Young?’Don’t let it bring you down, it’s only castles burning.’