Some really good sensible answer's, but for myself who has done single handed boating in the past was to prepare the lock first opening one gate, gently cruising in just enough momentum to reach the ladder, up onto the boat roof with my centre line, which in my veiw is paramount, for me climbing the ladder is the most dangerous part, a wet green slimy ladder where you must alway's take your time, and there could be more pressure on you if other boater's are around. I think if you are first to that lock, then it is "yours" and by right's no one else should touch the paddle's without your say so. I have seen some of these boater's at work at Kegworth Deep in the past, where boat's have been very nearly sunk,
I enjoyed single boating, but I have a wife now, so she operate's the lock's.
Good luck and enjoy.