Here’s a citation source: John Breeding’s The Wildest Colts Make The Best Horses (2006), p. 194 [http://bit.ly/2xCB07f]. I noticed that two other sources say it was from the 13 July 1958 edition of the Sunday Times, which is probably accurate, since it’s a Sunday; 13 June 1958 was a Friday. Two further sources say 23 July 1958, which was a Wednesday. Here’s a Google search that gives 8 results that include this page, the 5 dated sources I note above and a couple that only have the year: http://bit.ly/2wewH2v.