The third of six children, Nicholson was born in Te Awamutu in 1961 and was brought up on a farm in Kihikihi in Waikato. On leaving school, he joined his brother, who was retraining racehorses and rode for local racehorse trainers. Nicholson journeyed to England in 1980 aged 19 and his first job was grooming for Mark Todd and Southern Comfort at Badminton (which they won). Within four years Nicholson had been selected for the New Zealand team for the 1984 Atlanta Olympic Games.

At Atlanta, where Todd won the Olympic three-day eventing gold medal on Charisma, Nicholson finished 28th on Kahlua. Like Todd, Nicholson based himself in England, where he enjoyed continued success as a rider and horse trainer. He really announced himself on the world stage when he was a member of the New Zealand team – riding Spinning Rhombus – that won the world team title at Stockholm in 1990.

Nicholson had a mixed time of it at the 1996 Atlanta Olympics. He and Buckley Province didn’t fare too well in the individual event, and the horse had to be retired. But in the team event, Nicholson, riding Jagermeister II, played a big part in the New Zealand team securing the bronze medal.

Though selected for the 2000 Sydney Olympics, he had misfortune with his horses and did not ride. By the time of the 2004 Athens Olympics, Nicholson was one of the elder statesmen of the New Zealand team. He finished 61st in the individual section at Athens and the New Zealand team was fifth.

At Beijing in 2008, he was eliminated after a fall while riding Lord Killinghurst in the cross-country section of the individual event, but in the team competition helped the New Zealand team to fifth placing. Nicholson was still in the New Zealand team at the 2012 London Olympics. It was his sixth Olympics, and the seventh he had been selected for. At the time, he was ranked No 1 in the world. He was named the equestrian section captain and rose to the occasion, riding superbly. Riding Nereo in the individual competition, Nicholson was 21st after the dressage, ninth after the cross-country, sixth after the first show-jumping round and finally finished fourth, missing the bronze medal by a whisker. In the team event, his efforts pushed New Zealand into a medal position. He then had a clear show-jumping round to seal the bronze medal (behind Germany and Britain).

Besides his Olympic silver medal and two bronzes, Nicholson has enjoyed plenty of success elsewhere. There was WEG team gold medal in 1990 and individual and team bronzes at the 2010 WEG in Lexington, United States, his sixth world championship. In 1998 he was placed fifth in the WEG individual event in Rome, with three New Zealanders, Blyth Tait, Mark Todd and Vaughn Jefferis, finishing ahead of him. Riding Nereo, Nicholson finished third at Badminton in 2013 (and 11th on Avesbury). It was another near miss for the man who by 2013 had contested the event a record 33 times. He was second on Lord Killinghurst in 2004 and there occasions when he looked set for the title but missed out. In the other major event of the eventing world, Burghley, Nicholson has been supremely good. He won in 1995 (on Buckley Province), was second in 1996 (Cartoon II), third in 1998 (Hinnegar), won in 2000 (Mr Smiffy), second in 2001 (Mr Smiffy), third in 2003, 04 and 05 (Lord Killinghurst each time), second in 2011 (Nereo), won in 2012 (Avebury).