After the death of his mother in May 1971, family commitments led Frith to move back to Sydney. Here he sought, to no avail, a full-time cricket related post but, thanks to a recommendation by Jack Fingleton, he did secure some work with the Australian News and Information Bureau. The return to Australia would prove to be short-lived and he moved back to the United Kingdom departing aboard the TSS Fairstar on 19 March 1972.
Commencing with the November 1972 issue, he succeeded Tony Pawson as deputy editor of The Cricketer before becoming editor from the March 1973 issue. He founded Wisden Cricket Monthly and edited it from June 1979 to February 1996. In 1988 Frith won the Sports Council's British Sports Journalism award as Magazine Sports Writer of the Year.
Specialising in Ashes Test match history, Frith has written dozens of books on both cricket in modern times and cricket of the past. His major works include My Dear Victorious Stod (a biography of A. E. Stoddart), a lavishly illustrated history of England versus Australia, Silence of the Heart (on cricket's suicides, an expansion of his earlier book By His Own Hand), The Fast Men, The Slow Men (about fast bowlers and spinners respectively), Pageant of Cricket (the only cricket book to have as many as 2000 pictures), Caught England, Bowled Australia (autobiography), The Trailblazers (the first English tour of Australia, in 1861-62), The Archie Jackson Story (biography) and Bodyline Autopsy. The catalogue of his vast collection ran to 1100 pages. He has also been involved in producing cricket videos, which have been extremely successful.
Frith famously commented that India should withdraw from the World Cup if they didn't improve. When they won it in 1983 he was pleased to (literally) eat his words, with the help of some red wine, claiming that he had helped spur India to victory..
In 2003 Frith became the first author to win the Cricket Society's Book of the Year award three times, and was also a finalist in the William Hill Sports Book awards for his Bodyline Autopsy. The book also won Wisden's book of the year and, in January 2010, it won Cricketweb's award for "book of the decade". In his assessment, Martin Chandler wrote:
"Autopsy" is a magnificent book possessing a vibrancy and objectivity that when I first read it I found quite remarkable. It is, without question, the CW "Book of the Decade" and were there any prospect of my being around to collect I would certainly place a large wager on whoever is writing this feature in 90 years time confirming it as CW "Book of the Century".
His co-written history of the Australian Cricket Board won the Australian Cricket Society book award in 2007, and in 2011 Frith was given the Cricket Society's Ian Jackson Award for Distinguished Services to Cricket.
He has been honorary vice-president of the Cricket Memorabilia Society since its foundation in 1987.