I feel like we rarely see old ladies on our TV screens any more. Most of the crime solving, superhero, TV cops, for example, are men. If you do get a crime busting woman, then the chances are she's either Scandinavian or implausibly sexy and stylish (or both) - and either way there's no chance she's what you'd describe as 'old'.
And yet, I grew up at a time when Ms Marple was without doubt the smartest person on the telly. Thanks to her sleuthing, the murderous villains of St Mary Mead were safely locked behind bars every week. Ms Marple always came good, solving the mysteries single handed, faster than whichever hot shot young detective Scotland Yard had assigned to the case, despite always having to deal with the doubts and prejudices based on her age and sex.
Well, a couple of years ago I encountered my own Miss Marple and have made a film about her for the telly. She's a 69 year old lady called Scott Engstrom who breeds Appaloosa horses in New Zealand. Scott emailed to tell me that I had overlooked a very important clue in the search for the origin of the Appaloosa horse. To be honest, until then, I hadn't realised I was looking for it.
A couple of years previously I made a TV show Around the World in 80 Trades in which I traded different things in foreign lands - coffee in Africa, chilli sauce in India, surfboards in China and then horses in Kyrgyzstan. Then out of the blue comes the email from Scott informing me that one of those horses, that I'd sold to a Kyrgyz farmer for $600, looked exactly like one of her Appaloosas.
A bit of research quickly revealed that all the history books written about the Appaloosa horses of North America agree they were imported by the Spanish Conquistadors. So they're European horses. Nothing at all to do with Kyrgyzstan or indeed Asia.
With that in mind, I discounted Scott's email as the ramblings of a crazy old lady and got on with my life. But the emails kept coming. And coming. Until eventually I was forced to look again at what she was saying.
Scott thought that my $600 horse might prove a theory she had held for years; that the history books were all wrong and that the Appaloosa actually came from Asia.
Take a look at a map and you'll see that what she was saying was, however at odds with everyone else, technically and geographically at least plausible. But if it were true then it would mean that everyone else, who had ever written anything I had read about the history of Appaloosa, was wrong.
So, we had a mystery to solve.
In 2012, Scott and I went to Kyrgyzstan to discover if her theory held up. It was a journey that took us into the Tien Shan mountains, over a 4200m high mountain pass in search of a lost valley populated only by Kyrgyz nomads and their indigenous horses. Despite being 69 and not having ridden a horse for over 10 years, Scott made the arduous journey in search of the DNA evidence she needed to prove her theory.
The film I've made, Secret Horse: Quest for the True Appaloosa, tells Scott's story; an older woman who felt so passionately about something that she was prepared to put herself on the line. She is an inspiration to us all to follow your heart and never take 'no' for an answer. Because as a result of Scott's endeavours, the history of the North American horse has to be rewritten.
For my own part, I think about how hard Scott had to work to convince me to take her seriously. She's reminded me not to forget that the older generation still have fresh and vital ideas. Plenty of people laughed at Scott when she voiced her theory over the years. I'm as lucky as the residents of St Mary Mead that she persevered and gave me the chance to play a part in proving them all wrong.
Secret Horse: Quest for the True Appaloosa is on BBC4 Wednesday 21st January at 9pm