Zac Purchase: 'It will be the best rowing team we have ever had'

"Two hundred metres to go," instructs Zac Purchase. And then he starts commentating: "Here come Great Britain, the closing stages of the Olympic final, going for gold. You can hear the crowd now..."

On one bank of Eton Dornay lake, the immaculately sculpted venue for the 2012 rowing events, the scaffold outline of the grandstands is in place, on the other it's neatly stacked awaiting construction. Purchase starts rowing too, as if sparked into action by his own words, and our boat shoots forward, his power telling immediately.

"Can Britain catch the Kiwis?" wonders Purchase in his imaginary race and that, too, brings an immediate response. No. I've lost my stroke and our session ends tamely without an imaginary medal and Purchase pointing out the stand where his fiancée, Fliss, will be sitting on 4 August, the day when it will be very real indeed.

Purchase is 61 days from his second Olympic Games, and a further eight from racing on these waters for a second Olympic gold medal. As suggested by his on-board commentary – an endearing moment that anyone with any interest in sport has surely indulged in – it is a prospect he is relishing.

"It's hugely exciting," says Purchase, now sitting in the clubhouse eating chocolate cake. "It's nice to have it in the back of your mind and allow yourself to imagine, allow yourself to get distracted by the grandeur and the fanfares."

Purchase's quest for gold, which he will make in company with his Beijing partner Mark Hunter, will be accompanied by considerable fanfare and could provide the grandstand finish to Britain's best Games on the rowing lake for more than a century.

That final morning at Eton will first see the coxless four, long Britain's flagship, go for gold followed by Hunter and Purchase – both boats are already favourites. If eachis triumphant it will equal half Britain's most successful gold return – in London in 1908 they won four.

"It will be the best rowing team we've ever had," says Purchase and proposes Katharine Grainger, three times a silver medallist, and Anna Watkins and the men's four as a couple of other likely gold-winning crews. There should be others, too, on the evidence of the opening World Cup event in Belgrade where Britain took a dozen medals, one from every Olympic class. "We won't be winning medals in every event – more crews have got to come in," says Purchase. "But we know we have the potential to do really well."

Today at the World Cup's second round in Lucerne, Purchase and Hunter face New Zealand, their likeliest Olympic challengers, for the first time this season, but it will take some power shift for Hunter and Purchase, the world champions, not to line up in London as favourites. "Basically, we're going to be sitting on the start line thinking, 'Don't fuck it up'."

Four years ago, Hunter and Purchase won the World Championships and every World Cup race in the build-up to Beijing. By the time of the Games they were hugely fancied and on Lake Shunyi they lived up to their billing – they led all their Olympic races from start to finish.

Purchase stood on the podium and cried. "The most emotional part was seeing the flag go up," he recalls. "It was a collection of weird, wonderful and amazing emotions. The ultimate one is disbelief because you've finally achieved the dream that you set out for. There is so little actual chance of making it – it's something like a one-in-60,000 chance of being an Olympic gold medallist. It's a pipe dream."

It is a long way down from that high, especially so for rowers who endure a mental and physical intensity and rigorously demanding schedule that few sports demand. Both Hunter and Purchase suffered afterwards. "There's nothing, a complete void, and that is actually really hard to cope with. It's a bit like being in the doldrums – you have to have that medal around your neck to make it worthwhile."

Hunter thought about giving up but Purchase, nearly eight years his junior, had no doubt that he would do it all again. "All you have to do is think about the Olympics and racing again. I live to race, I absolutely live to race. I wouldn't be in a sport for as long as I have been if I wasn't winning because I derive a huge amount of impetus through the winter, the horrible hard slog, from those wins. At the end of a day you can sit down and think what I've achieved today will help me win in the summer."

British Airways, the official airline of the London 2012 Olympic and Paralympic Games, is proud to support Zac Purchase