Kirsty Wark’s diary: On the Caledonian sleeper, the new Donna Tartt, and a week of Edinburgh shows

There isn’t a Scottish politician in living memory who hasn’t been on the Caledonian Sleeper. I always imagined Donald Dewar folding himself up in his berth, he was so tall. He was notoriously sniffy about the company he kept in the bar and once recounted the horror he felt when — stuck in snow — he was forced to fraternise with practically the rest of the Labour front bench for 22 hours somewhere south of Carlisle.