The former English national champion of Austro-German parentage and the former English national champion brought up in China have not spoken to each other for a long time. Indeed, last year at the world championships in Tianjin they almost came to blows - and certainly would have done, had they not been held apart.
It is partly a tribute to Alan Ransome, the British team manager, and Donald Parker, the coach, that things have been as satisfactory as they have. Prean nearly beat Andrei Mazunov, the former European silver medalist, in the men's singles round-robin phase. Chen, with victories over Sule Olaleye of Nigeria, the African champion, and the Canton-born David Zhuang of the United States, did extremely well to keep alive Britain's slight medal hopes for three days.
The question of how these two could possibly room together had been troubling Ransome for some time. "The last thing we want is for either to have aggravation before they play," he said.
But they were lucky. Chen became stranded in his home province of Fukien, where he had been preparing for the Games, and arrived six days late, by which time Prean was peaceably sharing with Parker.
By the time Chen's extraordinary escape - occupying 40 hours of travel via Hong Kong, Singapore and Frankfurt - had been completed, there were only two days to go before the first match. The exhausted 36-year-old was bundled into a room with one of the British cyclists and order was maintained.
Yesterday was the first time they had been scheduled to play at similar times. Prean lost 21-6, 21-7 to Vladimir Samsonov, the much-improved world number 10 from Belarus, whom he needed to beat to have hope of survival, and Chen failed to upset yet another Chinese expatriate, Johnny Huang, the Commonwealth champion from Canada, losing 21-12, 21-14. But neither Briton spoke to the other as they suffered elimination.
There is little chance of patching up a rift, whose origins were six years ago when Chen was first selected for England. That deposed Prean from the top spot and his father, John Prean, the then English chairman, has maintained a bombardment of criticism for much of the time since.
Carl Prean, apparently convinced by Chen's maverick tendencies that he had been ill treated, and incensed by the way the management allegedly treated their tiff in Tianjin, has succumbed to the same mood.
But a solution is likely. Chen, after defeating the Chinese veto that stopped him representing Britain in Barcelona and after a decade and a half at the top, is retiring. This was his first and last Olympics, and this week is his last in the game. Prean has a chance of being top dog again.