The question harked back to the difficult choices Grobler had made prior to the London 2012 Games in switching his two top men from the pair, Andy Triggs Hodge and Pete Reed, into the four after three gallant but vain years of attempting to beat the New Zealanders who would claim the London, and indeed Rio 2016 gold, Eric Murray and Hamish Bond.

History records that Grobler's decision paid off. 

Triggs Hodge and Reed returned to the boat in which they had won gold at the 2008 Olympics and helped defend that title for the home nation. 

And after similar calculations four years later, they would be a part of Britain's winning eight at the Rio 2016 Games, adding to the gold already won by a more youthful four.

Pre-noise, Grobler had explained: "Before London 2012 we tried for three years to be the best in the pair, with Andy and Pete. We gave the New Zealand pair some good races, we tried everything we could. 

"But as a coach sometimes you have to be realistic.

"In the end we moved Andy and Pete to the four, and of course we defended the gold. 

"But it is never an easy decision. Because you are looking at guys already in the four who were world champions in 2011. People might look at that and say 'the silver is safe in the pair, and maybe if there is a mistake made you will have gold. And the four could win another gold'.

"But I think in hindsight the big jump the Australians made with their four at London 2012 meant it was a correct decision. Otherwise we could have ended up with two silvers."

There was a momentary silence.

"And that would be…"

Cue alarming noise. Germanic. Perturbed.

"…disaster for British rowing!"

The reaction tells you why Grobler has supervised so much victorious activity in his main personal role coaching men's openweight rowers.

Here is a man who knows the fine lines between silver and gold, having directly guided 12 East German and British crews to the latter at the Olympic Games since Montreal 1976.

Calling time on the Triggs Hodge and Reed doubles project - something he had done with similarly effective results with Matt Pinsent and James Cracknell before the Athens 2004 Games - was just another logical move for the man who established himself as a coach in the triumphant, but now tainted environment, of the East German sporting establishment.

It could be argued that Grobler's record makes him the greatest coach in British sporting history. Indeed, that claim is expanded on in a book published this month, More Power - The Story of Jürgen Grobler, The Most Successful Olympic Coach of All Time.

Grobler, who learned his discretion in the brutal environs of a Communist regime that demanded obedience, did not offer his collaboration with this book.

But it is a measure of the respect in which he holds the two authors - Hugh Matheson, who rowed for Britain in the 1972, 1976 and 1980 Olympics before covering the sport as a journalist for, among others, The Independent, and Chris Dodd, rowing correspondent for The Guardian since 1970 and an outstanding historian of the sport, that immediately after informing them of this decision he invited them to join him for extended drinks at a nearby bar.

Matheson - who took silver in the eight at the 1976 Montreal Olympics behind an East German crew that was revealed to have been part of a state-sponsored doping regime of which Grobler, whether he liked it or not, was a part - and Dodd know the sport inside out. And their joint venture tells Grobler's story with a weight of knowledge. If you want to know how it was, enquire within…

The questions apparently not asked of Grobler when he took up coaching in England - initially at the Leander Club - in the wake of East Germany's political collapse were asked very pointedly seven years later in 1998 when thousands of documents meticulously kept by the Stasi - East Germany's secret police - came to light, covering doping and informing.

This book weighs the issue thoroughly but - despite Matheson's Olympic experience - without an agenda. As a result of these newly publicised documents a total of 113 sports coaches and officials were investigated by the Berlin public prosecutor's office as former athletes in some cases called them to account for lingering physical and mental problems their regime had created.

No rowing coaches were on the list. A year later, the figure of preliminary enquiries being undertaken by the prosecutor's office numbered 17.

Matheson himself reported at the time for The Independent that Grobler was one of many within sport who had been made an informer by the Stasi, but he concluded "it is very hard to see that anything harmful was passed on or that any damaging consequences followed".

“He was, as he has claimed, a minor player in a system that enveloped the entire society and from which no-one escaped as both informer and victim," he added.

Grobler was interviewed at that time by Michael Calvin for the Mail on Sunday, and commented: "Some things that were going on at that time were not correct, but I can look everybody in the eye and not feel guilty…you must understand that thousands of people were contacted. I wanted to leave Germany because I wanted to prove I could succeed in a different system."

Grobler's results before and after this statement, painstakingly chronicled, provide unarguable confirmation that he has managed this second career challenge.

After earning his second Olympic gold under the German's guidance at the Rio Olympics, Triggs-Hodge described what the coach did as "genius at work".

Others, such as Phelan Hill, who coxed the British eight to gold in Rio, enumerate some of Grobler's more tangible virtues: superb planning; clear judgement; endless attention to detail.

Regarding the latter quality - Grobler maintains a close relationship with the German boat manufacturers Empacher and has fine-tuned designs according to crew requirements, for example when Hill wanted four speakers to be added to the eight boat at the Rio Games, as well as an extra lip around the side to prevent water splashing in during a crosswind.

But it is the human side at which Grobler has proved masterly - for instance, in managing the huge talents of Steve Redgrave through the vicissitudes of colitis in 1992 and type two diabetes in 1997, afflictions that would have seen an immediate end to his career had he been in the East German system.

Grobler, by so many accounts in this book, is fundamentally honest with his rowers, hugely loyal, but also practical and at all times unsentimental.

According to Hill, he never demands certain ergo scores in the gym. He knows his rowers well enough to know that they will be working hard enough for that themselves.

"If anything," Hill says, "Jürgen will tell people to back off. He'll walk round the ergo room and then just look at someone, gain eye contact and gesture to slow down…he has the sensitivity of knowing when to push people and when not to. He's always managing things."

Grobler may eventually decide to tell his story in his own words. In the meantime, however, this richly knowledgeable account does an excellent job on his behalf.