then in existance. The militias were not permanent forces,like the army, but were "embodied" or called into service only at times of war of national emergencies and disbanded when the war or national emergency was over.

Mr Weston would have joined the Surrey Militia, as a "native of Highbury", which was in that county. Militias were organised on a county basis, note.

According to my copy of The English Militia by J R Western, the county militias were not embodied between 1783 , when the Treaty of Paris concluded hostilities with the United States of America and France and December 1792, when the militia were once again embodied in preparation for the war against revolutionary France.

See this definition from the OED:

Formed or combined into a militant body or company; arrayed, marshalled.

And here are the date relative supporting quotes:

1667 MILTON P.L. I. 573 Such imbodied force, as, nam'd with these, Could merit more than that small infantry.

1715 POPE Iliad II. 540 Not less their number than the embodied cranes.

1798 MALTHUS Popul. (1817) II. 11 The number of embodied troops.