This England team are the most organised and prepared in the world. Every individual player knows every individual weakness of every opponent, and how best to exploit it. Thanks to the tireless work of Andy Flower and his team of analysts, England are one step ahead before a ball's even been bowled.
Consistency on two levels - in terms of performance and in terms of selection. England are now far less likely to take their eyes off the ball and have a shocker in one test, which has led to far greater performances throughout. And the consistency of selection has seen players in poor form being nursed back into shape, and ultimately pushing England to the top spot.
3) Strength in depth
Luckily this strength hasn't had to be used too often thanks to not many injuries, but as and when the situation has required, players have stepped up and performed. When key players have retired or been unavailable, there have been ready made replacements who've come in, and the county production line is incredibly strong at the moment, which can only see this strength continue going forward.
Every successful team needs a bit of luck, and England have had plenty. Their best team in donkeys years has come at a time where the traditional best teams in the world have been rebuilding and not offering as strong an opposition. Plus they've seen opponents lose key players to injury at crucial times, which has certainly helped.
5) They have the best players
It may seem an obvious one, but to win games of cricket you need to be generally a better team than the opposition, and more often than not England are putting out man for man better players. Throughout their batting they are immensely strong, and their fast bowling options are an embarassment of riches. They have the best attacking spinner in world cricket, as well as a captain and coach that brings everyone together to get the best out of them. It's no wonder that with all of that happening that England are the number one ranked team in the world. And that might not change for a long time.