Manthorp was born and educated in England, but considers himself very much a South African. When he was a year old, his parents emigrated from the North of England and Manthorp spent his formative years in South Africa before returning to England to complete his schooling. With South Africa isolated in sport due to apartheid, he stayed on in Britain and began his journalistic career in 1986, commentating and writing freelance.
With the end of apartheid in 1990, he decided to return to South Africa, where he set up his own sports agency, MWP Media, in 1992.
He has stayed there ever since, apart from the necessary travel required to follow sport, which has taken him to all the cricketing corners of the world.
He has covered more than 40 tours and 120 Test matches since South Africa's return to international cricket and Zimbabwe's elevation to Test status.
He is a regular commentator for SABC radio and television and has also joined the host radio teams in West Indies, New Zealand, Australia and England. He writes for newspapers and magazines and recently completed his fifth book "The Proteas: 20 Years, 20 Landmark matches" marking the 20th anniversary of South Africa's return to international cricket.
As well as cricket, he also writes on golf and rugby.
Gazza: the Gary Kirsten biography
The Beer Drinker's Guide to Losing Weight, (with Paddy Upton), The Penguin Group (SA) (Pty) Ltd, ISBN 0-14-027225-9
Graeme Smith: A Captain's Diary 2007-2009, Jonathan Ball Publishers, ISBN 978-1-86842-353-8
Taking the Mickey: the Mickey Arthur biography, Jonathan Ball Publishers, ISBN 978-1-86842-383-5
The Proteas: 20 Years, 20 Landmark Matches, Burnet Media, ISBN 978-0-9870058-1-6
Bouch: Through My Eyes, Jonathan Ball Publishers, ISBN 978-1-86842-590-7