Alastair Cook has expressed his delight at reaching 20 Test centuries for England following his unbeaten knock of 114 on day one of the first Test against South Africa at the Oval.

Cook's impressive display at the crease helped the hosts post a commanding score of 237-3 as the two teams battle it out to be named the world's number one Test side.

"It was a slow wicket and you had to work hard for your runs," he told Sky Sports News. "To lose three wickets on the opening day is a good effort.

"Any hundred is important - especially to go from 19 to 20. There were a couple of 94s along the way, which has been slightly frustrating, and it's also a big series as well so to start well was important."

Cook, 27, is the second youngest player to reach 20 Test hundreds behind India's Sachin Tendulkar.