In the larger towns the division into wards, with a separate police system, can be traced at an early time, appearing as a unit of military organisation, answerable for the defence of a gate of the town. The police system of London is described in detail in a record of 930–940. Here the free people were grouped in associations of ten, each under the superintendence of a headman. The bishops and reeves who belonged to the "court of London" appear as the directors of the system, and in them we may see the aldermen of the wards of a later time. The use of the word "bertha" for ward at Canterbury, and the fact that the London "wardmoot" at a later time was used for the frankpledge system as well as for the organisation of the muster, point to a connexion between the military and the police systems in the towns.