comes to a gene, which is only two nanometres wide, the answer is “nothing”; they work by inferring from expe riments on things that they can see. As she says: “It is the „unseeable‟ nature of molecular biology … that makes it so difficult to grasp.” She quotes one of her scientists, Peter Hall: “it‟s based on faith, ultimately.” And even when scientists have a go od sense of what their experiments are telling them, they‟re up against the fact that life is an immensely complicated process: we can land a probe on a distant comet after a 10-year flight because the Newtonian clockwork of bodies in space is predictable. But all-embracing laws of biology are hard to find. The process of discovery goes like this (and p53 is a classic example): something unexpected and odd turns up; investigation begins; its character gradually becomes clearer but its purpose remains a mystery; then evidence accumulates to suggest a function. That evidence is often misleading and, in the case of p53, a function diametrically opposed to the true one was ascribed to it for 10 years: it was thought to be a cancer-causing protein. Then came the moment of clarity and the potentially great unifying principle was born: in 1989, P53 was revealed as the master tumour suppressor – an order was established at last. There are great hopes that our knowledge of p53 will lead to novel cancer treatments, but the pattern has grown much more complicated since then. In some situations p53 can cause cancer. For cancers to grow they need a mutated and disabled p53: in science, these cycles of discovery go on forever, and so will the battle between cancer and p53. But progress is being made. One of the brightest hopes for therapy using p53 is in families with a predisposition to cancer. The reason for this blight is that the family members have each inherited a mutant copy of p53 and are therefore without the normal protection it provides. An experimental gene therapy (Advexin) already exists to correct this, but in 2008 the US regulatory body refused to license the treatment. A similar product, Gendicine, is licensed in China and approval for its clinical use is being sought in the US. One common story in today‟s medical research is of remarkable possibilities constantly being blocked by a sluggish regulatory system and the skewed priorities of Big Pharma, which prefers to develop bestselling drugs that will have the widest use. Armstrong‟s book will offer many readers a sense of hope, but might also induce intense frustration at the long time it takes for discoveries in the lab to filter down to hospitals and the marketplace. Nevertheless, we can be sure that p53 , even if it is not the “cure for cancer”, will have an honourable role to play in our attempts to find one.