South Africa captain Graeme Smith has said that he is aware of the hard work that is required for his side to remain top of the world Test rankings.

South Africa rose to number one in the world after the 2-0 series win against England and Smith has said that they need to improve to stay there.

"We will face different challenges but we have a formidable squad that performed outstandingly well here," The Telegraph quotes Smith as saying.

"We need to grow that. We are a humble team. We are not flashy and it will be about hard work."

South Africa also top the Twenty20 world rankings, just one point ahead of England.