Quote Originally Posted by Heidrek
I did notice that Britain was cut off from mainland europe
Get a sense of persepctive, Heidrek, what you meant to say was:

"I did notice that europe was cut off from mainland Britain"

But yes, if your sea lanes are blockaded it effectively cuts the lines of communication from your king to your provinces across the water, and loyalty is very dependent on the distance (or rather travelling time) of the king to the province. A sea blockade can be very very bad as it cuts the king off from a lot of provinces at once - this always has to be a major consideration when starting wars with a naval power. I usually make sure Britain in particular is well garrisoned and able to look after itself in terms of maintaining loyalty, as you never know when Europe may be isolated

Getting your king stuck on an island with no port is one of the most challenging situations of all.... and as has been mentioned above, a king going on an attack also "cuts him off" from the empire at large. Ideally your king should sit in the middle of your empire so his travelling time all round is fairly even, but certainly moving him from one end to the other will have noticeable effects on loyalty at either end. Otherwise, if you have good naval supremacy he can sit in a port province, and have a good "reach" across the empire by sea, but this is vulnerable when new wars start