Non conformity - many English Catholics refused to attend the new, more Protestant like services (recusants)
Revolt of the Northern Earls, 1569 - Catholic earls wanted to remove Elizabeth, make MQS queen, held a Catholic mass at Durham cathedral, got as far as Leeds
Threats from abroad - Pope, France, Spain - strong Catholic countries that wanted to restore Catholicism in England
Elizabeth listened to the advice of a navy leader John Hawkins who told her she needed to improve her Navy. She had done this months before the invasion