What causes a loss of power in brakes on a 1991 jaguar sovereign?

my near side wheel bearing went a few days back and my brakes did not work that well at all.so it could be a wheel bearing which is easy to check.jack the car up try and shake the wheel it by holding the top and bottom if it moves then your bearing/s need replacing which is easy.this was my problem any how.replaced them both and its fine now.