"By then the army people had arrived and the anti-terrorist people had arrived with little guns, they looked like toy guns. We were put on a bus."
Mr Robertson tried to follow what was happening on television, but as it was all in German, did not really know what was going on.
It was unlikely that would happen today with the security measures in place and easier targets like shopping malls, Mr Robertson said.
Things have changed since his day. When his son-in-law Eric Murray won gold in 2012 in the coxless pair with crewmate Hamish Bond, he was rewarded with an Audi.
Mr Robertson got a box of Milo.
"When I was rowing it was purely amateur. We actually helped fund the trip - we had to pay some of the money to go to Europe. These days, it's a full-time job for them - all they do is row."
He told the students about starting rowing at 15 in Oamaru and working his way to the international competition.
After seven years of rowing throughout the season and going to national championships, Mr Robertson made the national team and moved to Christchurch, where he had to train for three months - twice daily except Saturdays, which was four training sessions.
"I was in the New Zealand eight for three years. The culmination of that was the race at the Olympics.
"In my rowing career, that was the big highlight. We trained hard and worked hard."
Mr Robertson rowed for about 10 years and has spent the last 20 or so years as a coach.
"I still coach rowing now because somebody helped me and I got a lot out of it. If I help now, maybe one or two out of that lot will get something out of it and enjoy it."
