Mention two advances in bowling that were pioneered by Pakistan

Mention two advances in bowling that were pioneered by Pakistan. Why did Britain and Australia view them with suspicion?

Pakistan has pioneered two great advances in bowling in response to sub-continental conditions. First is ‘Reverse swing’ to move the ball on dusty, unresponsive wickets under clear skies. Second is ‘doosra’ to counter aggressive batsman, who were threatning to make spin obsolete.
Britain and Australia viewed them with suspicion because they considered it to be under handed and illegal bending of laws of cricket. But later on it was accepted as it was realised that laws of cricket could not continued to be framed in favour of British and Australian conditions of play. Hence it became a part of cricket everywhere in the world.