Christiansen, who juggles her sporting heroics with a City career with Goldman Sachs, defended her Grade 1a championship title ahead of British team-mate Anne Dunham, who took silver.
Their success, allied to Natasha Baker’s victory in the Grade II event, helped Paralympics GB retain their team crown and kept Christiansen on track to repeat her London 2012 golden hat-trick.
“I always want to do my best at everything I put my hand to – whether that’s academic work or sport,” said the 29-year-old, who goes in Friday’s freestyle competitions.
“It’s going to sound big-headed but I think you have to have more than talent to stay at the top. Ask my carer – I’m so meticulous, I time my days down to last second. This is surreal at the moment. I’ve had a change of coach and injury after injury. Up until last week, I didn’t even know which horse I would be bringing.”
Baker – dubbed “the horse whisperer” because her lower-body paralysis means she has to guide her mount by sound alone – defended the title she won at London 2012.
Jeanette Chippington, a 12-time swimming medalist before taking up canoeing, won the women’s KL1 event at the age of 46 to herald a golden afternoon for Britain at the Lagoa Stadium.
Emma Wiggs, who represented GB in sitting volleyball at the last Games, won the KL2 final, while 49-year-old Anne Dickins completed a canoe team treble by winning the KL3 event.
Sprinter Richard Whitehead added 100m T42 silver to his 200m gold.
Charlotte Henshaw won bronze in the 100m breastroke SB6, with four-time Paralympic champion Ellie Simmonds sixth.
Weir announces retirement
Paralympics GB great David Weir has revealed that he intends to bring down the curtain on his wheelchair racing career next year as he comes to terms with a disappointing Rio 2016 Games.
Weir failed to defend his 800m T54 crown on Thursday, finishing sixth in the last of his individual track events.
It followed fourth and fifth-place finishes in the 1500m and 400m and means he is yet to win a medal in Brazil this summer, having won four golds at London 2012 and two in Beijing four years earlier.
The 37-year-old has a final chance in Sunday’s marathon and also plans to bow out of competition at that distance in London next April.
“The sport has evolved over the last four years and I’m just not good enough,” said Weir, who has won a record equalling six London Marathons.
“This is definitely my last race on a track individually and I didn’t come away with a medal. Next year’s London Marathon will be the last race of my career. I’ll still do the marathon here on Sunday and I’ll talk to the team about the relay to see what’s best.”