We speak proverbially of needles in haystacks, yet that is a relatively simple search on the scale of things. Needles have many different properties from hay. Imagined strategies might include burning the haystack and blowing away the ash, dumping it in a swimming pool and observing the only item to sink, or passing the hay over a magnet. In this revealing 'More or Less' broadcast from the BBC, Tim Harford looked at the probabilities of finding , not a needle, but a slightly different piece of hay in a haystack, with contributions from Dame Stella Rimington, Howard Wainer and Louise Amoore. The Maths of Spies and Terrorists "But how feasible is it for the security services to follow all the people on their watch list?" Should you wish to start exploring the world of mathematics in relation to low-probability, high-consequence events, 'Risk and the War on Terror' is no bad place to start; even though it was first published six years ago. In Amoore's (one of the editors) introduction, she states, "Risk-based calculative models and practices are emerging as a key means of identifying vulnerable spaces and suspicious populations in the war on terror. The imperative to "connect the dots" means that all kinds of new data analysis programs are being developed and implemented across the public and private sectors, such as automated screening programs, financial risk assessments and telecommunications link analyses." This discipline is affecting fields as diverse as mortgage applications and policing. Aside - I still remain fascinated by the observation that the number of rubbish skips in a London street was a reasonable predictor of future property values in the area. The programme which started this post, wherein Tim Harford explored the quantitative difficulties inherent in identifying the risk subject, leads to an eventual problem. The more successful the algorithms in identifying potential terrorists, the more at risk will be those people who do not fit the predicted pattern. There will be an inevitable increased risk for Caucasian grannies and children being coerced to carry items through airports. This leads me to what has become known as the 'Baraza-Kerubo Village Market Incident', wherein it might appear that the then Kenyan Deputy Chief Justice, Nancy Baraza, might have strongly objected to being searched. If you have lived or worked in a city or country where there is a 'kila siku' threat from the bomb or the bullet, it might be suggested that one might want to be very visibly frisked along with everybody else, to protect oneself against the possibility of terrorist coercion. Put very simply, if you have to join the queue like everybody else, there is less risk that the kidnap of your child or spouse could be used to influence you to take a package unchecked through a security screen. I cringe at what I now see as my naïveté. In the 80s I enjoyed it when a car could drive across the tarmac and collect me directly from the plane. OK, it felt cool. It was stupid. It put me, and more importantly other people, at substantial risk  should any 'undesirables' have found out that I was bypassing the queues. So, am I likely to win the lottery tonight? Yup, I fit the profile, human, resident in ...