OK, going to fess up to this one...
I went to start the Triumph only to find that it made a click noise but wouldn't turn over. The battery on the 999 is always going flat so I naturally thought the same had happened to the Triumph as I hadn't riden it for few days. Wrong! You have to pull the clutch in or the starter won't turn. It's only my daily commute bike and I had forgotten. Duh.