I would have liked to have spent a couple of days in San Francisco after my conference finished — long-term readers will know that I spent a fair amount of time in Fog City in the noughties but it's been over six years since my last visit. Sadly, though, I had to make do with six hours. However, it's hard to complain too much when it was such an unseasonably warm, sunny day and the city was as beautiful as I remembered.

When I left Washington early on Wednesday morning it was really, really cold, yet when I stepped off the plane in San Francisco six hours later, it was at least 20 degrees warmer and gloriously sunny. Flying across the country really emphasised how huge the US is, and how varied: the aerial views of the Rockies and the frozen fields of Wisconsin were particularly striking.