Riding Rosemary and Mark Barlow’s 12-year-old Avebury, the New Zealander went into the ring in second place and had one fence down, the final element of the treble at six.
This guaranteed he would take the runner-up spot, but gave the overnight leader, the USA’s Sinead Halpin, two fences in hand.
But this wasn’t enough. Sinead and her mother Bernadette Cogdell’s Manoir De Carneville hit fence three, fence nine and the second part of the double at 12 to drop to second.
This was Andrew’s third Burghley title but his first for 12 years.
“I’m not so surprised this time, but I’m highly delighted. It feels like 20 years,” said Andrew, who bred Avebury and sold him as a four-year-old to spend two years as a showjumper before he came back, initially for his partner Wiggy to ride.
“Avebury is amazing. He’s a joy to ride. We’ve had days where he’s let me down and days where he’s probably felt I’ve let him down, but he’s generally been consistent and to win here is the ultimate.”
Sinead said: “He warmed up beautifully. He was a bit tired, but I felt as prepared as I could have been going into that situation. I’m disappointed but I’m also proud of him – he tried really hard.
“We’ll go back to the drawing board and come up with ways to help him feel stronger in the air and another tool to help him when he’s just a bit tired.”
“This week has been amazing – I’m so lucky to have the horse and we’ll be back again and again and again.”
Britain’s William Fox-Pitt lowered two fences to hold third place on last year’s winner, Catherine Witt’s Parklane Hawk.
“He’s gone brilliantly all week and I couldn’t be happier with him. He can’t win them all – I’m saving it for Badminton next year,” said William, who will win the lucrative Rolex Grand Slam if he can triumph at Badminton 2013.
The home side’s Oliver Townend also recorded eight faults to hang onto fourth place with Paul Ridgeon’s Armada.
New Zealand’s Jock Paget, a recent team bronze medallist in London alongside Andrew, repeated his result of last year with Clifton Lush by taking fifth after one down. The USA’s Allison Springer was sixth on Arthur IV – up from seventh overnight despite two down.
British former young rider team silver and individual bronze medallist Izzy Taylor, a 29-year-old mother of two, made a fantastic Burghley debut to finish seventh riding the mare Briarlands Matilda. She had just four faults today.
German Kai Ruder’s one down lifted him from 12th to eighth with Le Prince Des Bois, while his compatriot Bettina Hoy jumped clear to move up from 16th to 10th on Lanfranco TSF. Australia’s Sam Griffiths moved in the other direction when 16 faults dropped him from fifth to ninth on Happy Times.
Third place today also secured William Fox-Pitt the $150,000 (about £94,544) first prize in the HSBC FEI Classics. Andrew Nicholson was second, with Allison Springer third.
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LAND ROVER BURGHLEY HORSE TRIALS FINAL RESULTS
1. Andrew Nicholson on Avebury (NZL) 45.8
2. Sinead Halpin on Manoir De Carneville (USA) 48.3
3. William Fox-Pitt on Parklane Hawk (GBR) 51.4
4. Oliver Townend on Armada (GBR) 51.5
5. Jock Paget on Clifton Lush (NZL) 52.2
6. Allison Springer on Arthur IV (USA) 57.2
7. Izzy Taylor on Briarlands Matilda (GBR) 61.3
8. Kai Ruder on Le Prince Des Bois (GER) 62.2
9. Sam Griffiths on Happy Times (AUS) 62.4
10. Bettina Hoy and Lanfranco TSF (GER) 63