Shield between English colonies and Spanish land.

Gibraltar.

Explanation:

Gibraltar was considered as a shield which is present between English colonies and Spanish land because this place is the last territory on which the Britain were occupied. First this area is the part of Spanish land but in 1713 Spain give it to the Britain after the war. This region is present between the boundary line of Spanish land and British colony which act as a shield. Now, it is a free state and have its own parliament.

the answer is they believed george iii would never give them their freedom.