 Further men were recruited from the Royal Irish Constabulary, London's Metropolitan Police and from the military presence in Shanghai itself, while a structure for recruitment of Britons in the United Kingdom eventually came about through the Shanghai Municipal Council's London agents, John Pook & Co. Once formalised, a steady stream of young men was recruited to serve in Shanghai.Promotion from the lower ranks of the force was, however, limited.Most of the force's commanders were recruited from British domestic or colonial police forces, although a cadre of young British men was recruited as cadets, and held senior ranks in the force in the 1910s-'30s.