Can any one tell me what an ESO is? My question relates to the War diary extract below. 17th May 1940: 1400hrs - Southampton Arrived at port of embarkation Southampton from Poole Dorset with 86 vehicles and 27 m/cs. 7 officers and 290 ORs. Vehicles parked in dock sheds under instruction of ESO and personnel embussed to rest camp āGā. Thanks