When I woke up this morning to see sunlight slanting off the blinds of my bedroom window, I was the happiest I'd been all week. All week I'd been plagued by interrupted sleep: like clockwork, around 5 a.m., I'd wake up for no explicable reason, and instead of drifting back into peaceful slumber as usual, I would lie sleepless and restless for an hour or more, till dawn crept up and the first buses and traffic of the day became audible, then I would finally snatch another hour or two of sleep...