From late October each year, bleary-eyed postal workers all over the UK sit in shifts, sifting through some 120 000 children's letters addressed to a rubicund, septuagenarian, airborne logistics expert living in the frozen Arctic. In accordance with guidelines, every letter is screened for signs of neglect, abuse or some other singularity. Every year, several escape the shredder. One year, a thoughtful 10-year-old wrote.