Readers of the 'brilliant Telegraph Letters page', as Ian Hislop recently lauded it, will be fondly aware of the eclectic combination of learned wisdom, wistful nostalgia and robust good sense that characterise its correspondence. But what of the 95 per cent of the paper's huge postbag which never sees the light of day? Some of the best letters inevitably arrive too late for the 24/7 news cycle, or don't quite fit with the rest of the day's selection. Others are just a little too whimsical, or indeed too risque, to publish in a serious newspaper. And more than a few are completely and utterly (and wonderfully) mad, such as the missives you'll find within these pages from someone who signs himself merely as ''''M'''', and believes himself to be the head of MI6. Now, the Telegraph gives the authors of these unpublished letters the stage at last. Baffled, furious, defiant, mischievous, they inveigh and speculate on every subject under the sun, from the rubbish on television these days to the venality of our MPs, from Kate Winslet's decolletage to this country's unhealthy obsession with marmalade. All those Telegraph readers who wondered if anyone else had noticed that the lunatics had finally taken over the asylum and sat down to write to their favourite newspaper to test the waters - they need howl into the void no longer. They are not alone.