Not as sharp as we once were

Coming to Oxford for a meeting, I took the opportunity to arrange a get together with two old friends. We were close at college and have kept in touch individually, but it's decades since the three of us had been together. As I approached our old haunt and saw the scene outside, I wondered briefly whether I might be too late. In fact T turned up shortly, hale if not hearty, but C never appeared and we did begin to worry a little. It turned out he was at home in London, convinced we were meeting the following night. My fault mainly. Once we ran the country, now it's buddy, can you spare a brain cell?