Could King George V force Britain into war?

Could King George V force Britain into war because he regarded Germany as a threat?

No; he could advise and object, but a constitutional monarch could not override the prime minister and cabinet if they chose neutrality.

George V could regard Germany as a threat and influence the debate behind the scenes. A constitutional monarch could not replace the prime minister's and cabinet's decision with his own. If Asquith refused intervention, royal anger would not itself mobilize the fleet. The political chain of authority therefore determines whether the naval counterfactual can begin.