[5] Gregson studied carpentry at TAFE NSW in Wollongong and has a degree in business and marketing from the Swinburne University of Technology.

[10] Gregson finished 4th in the 1500 metres at the 2009 Summer Universiade in Belgrade, Serbia, missing out on medaling by only 0.22 seconds.

[13] Gregson's first appearance in IAAF's brand-new Diamond League was at Eugene's Prefontaine Classic on 3 July, where he won the second-tier International Mile.

[14][15] Gregson next appeared in a Diamond League race on 24 July, in the Herculis meet at Fontvieille, Monaco.

He improved his personal best over 1500 metres by more than four seconds to 3:31.06 and finished 5th, beating among others former World Champion and Olympic medalist Bernard Lagat and breaking Simon Doyle's 19-year-old Australian and Oceanian record.