Groves speculates because he and Bullmer were professional watchmakers, rather than athletics people, they were more likely to be truly neutral, rather than having a vested interest in Snell setting a world record.
They used ordinary mechanical stopwatches, which in those days recorded times to the tenth of a second, rather than the hundredths used in the modern versions.
Therefore, because Snell broke the record by just that solitary one tenth, a fact celebrated in that Monday's Whanganui Chronicle as "an historic and colossal performance", Bullmer and Groves were subject to rigorous scrutiny.
They immediately took both watches back to their workshop, where they had to test run them for two hours to make sure there were no faults.
"Then the watches were sent to Wellington, as far as I can gather, before they eventually came back," Groves said.
"We weren't aware, I don't think, at the time that there was anything special about the race time."
Bullmer and Groves first met in 1945 when they were both instrument repairers in the Royal New Zealand Air Force, with Bullmer then taking him on as a watchmaker's apprentice after World War II.
Bullmer passed away in the 1970's, while Groves retired in Whanganui in 1989, before moving to Rotorua around 15-16 years ago.
"I'm still doing watch repairs and clock repairs."
He was interviewed, and thanked in the acknowledgments, by former runner and author Vern Walker for his 2014 book Peter Snell and the Kiwis Who Flew, which included the story of Snell's Whanganui run.
Along with Groves and Bullmer, the other time keepers that night were Colin Bailey, Jim Boswell, Wilf Broadhead, Ken Broughton, Terry Gilbert, Charlie Humphries, Norm Moosman and Doug Harris.
The international track meeting starts at Cooks Gardens at 7.15pm on Saturday, with the One Mile Championship being run at 9pm.
