I Consider it a great honour to be invited to deliver the First Lanchester Memorial Lecture, which, according to the instruction received from the Secretary of the Royal Aeronautical Society, should deal with Lanchester's personality and achievements. It is also a great pleasure for me to recall my personal contacts with this great man. On the other hand, I am not quite sure whether the decision of the Council, choosing me as the first Lanchester Lecturer, was really a wise one, since I am not in the best position to present a full biographical sketch of Lanchester. Somebody more familiar with Lanchester's automobile work, as, for example, Sir Harry Ricardo, would be more able to present a full picture of Lanchester's achievements. I must, therefore, restrict myself essentially to the treatment of Lanchester's contributions to the sciences of Aerodynamics, Flight Mechanics and Operational Analysis.