tiger Moth slats
other planes including some earlier jets had automatic slats. north american rockwell sabreliner 40 and 60...F86, A4
many planes had this nice feature...airspeed increased, slats retracted...based on springs!
ps
nigel, boeing flaps are really slow...douglas slats come out really fast. perhaps one reason boeing bought douglas. 2 seconds seems long for slats in this type.