Politicians love to berate GPs for failing to spot cancer symptoms, but it's very difficult to catch cancers at an early stage. If you take the case of ovarian cancer, its symptoms are incredibly nebulous: a little bit of bloating; tiredness; sweatiness; a change in bowel habits, perhaps. When such symptoms arise, usually when the patients are in their mid-40s, GPs don't scream: "This person has cancer, deal with it now." They more commonly suggest menopause or irritable bowel syndrome. Sometimes the cancer will masquerade as constipation, and it's often very difficult to find the difference.

Cancers can be hidden in the most mundane of symptoms, and often in ones that are not bothering the patients. A patient might come in with a confused story of miscellaneous symptoms, some of which are related to one condition, some to another. And the voice of experience whispers in my ear: "Listen to this story again. There's something in there that you're not getting." Sometimes it's just a throwaway comment that the patient makes as they're walking out the door. So you get them to come in and start again.

We can't have the American system of scanning and x-raying everything, because that's not good for the patients. You raise patients' anxiety levels, and if you start x-raying people the whole time, you could end up causing cancers. We also have to think of the cost: we do not have an unlimited pot of money. Moreover, if you're too focused on the minutiae of the tests, you forget to look at the whole picture, and you stop listening. If you listen hard enough to a patient, they will tell you what's wrong with them.

Dr Peter Swinyard is is a Swindon GP and chair of the Family Doctor Association