Morkel bowled the fastest delivery(173.9 kmph) in the history of cricket in the match against Royal Challengers Bangalore on April 16th, 2013, it is yet to be officially cited.
The Pervious record was clocked at 161.39 km/h (100.3 mph) and was bowled by Shoaib Akhtar of Pakistan during a match against England in the 2003 World Cup