Stewart thinks England can win back the Ashes
"If we can maintain form and fitness and in home conditions you never know," he told BBC Sport. "They're going from strength to strength. We've got to remember that Australia are the best side, there is still a gap between us but we've certainly closed that gap from when we last played them."
On the first Test, which South Africa lost by seven wickets on the fifth morning, Stewart thought that "England didn't allow them to play at their best. At the start of the series I thought there would only be one Test in it, but now I think we can win by more than that."
Stewart has been immensely pleased by Andrew Strauss's progress in the last seven months. "It's been incredible," he piped. "When you start in international cricket there's always that slight question-mark in the back of your mind, but he hasn't looked out of his depth at any stage. Now when he comes to the wicket he's full of confidence."