Jonathan Fox and Sophie Pascoe both set new world records this morning as the swimming got under way at the Paralympics with some blistering racing at the Aquatics Centre.
Fox lowered his own mark in the S7 100 metres backstroke while Pascoe, of New Zealand, cut the record she already owned in the SM10 200m individual medley.
Witnessing it all were Prince Albert and Princess Charlene of Monaco, the latter a former swimmer having competed for South Africa at the 2000 Olympics.
Swimming in front of a home crowd, Fox led from start to finish in his heat to take 0.59 seconds off his record in one minutes 09.86 seconds.
At almost three seconds faster than any of his rivals, the 21-year-old is a clear favourite to take tonight's title and go one better than his silver in Beijing.
He said: "I came to the heat looking to qualify first for the final tonight which I have obviously done.
"I didn't realise I had broken the world record until I looked up at the scoreboard.
"I had wanted to go under 1:10 for a very long time and this is really the competition to do it at.
"I'm very happy."
Pascoe lowered her own mark in the individual medley by 0.65secs to 2mins 28.73secs.
Charles Rozoy set a European record of 1:01.18 in the S8 100m butterfly with Kateryna Istomina doing the same in the women's equivalent - along with a new Paralympic mark of 1:11.04.
Jia Hongguang set an Asian record of 1:14.98 in the men's S6 100m backstroke.
Tamas Sors heads the S9 100m butterfly with world record holder Natalie du Toit leading the women's equivalent in her final Games.
Enrique Floriano, of Spain, heads the field into the S12 400m freestyle with British 16-year-old Hannah Russell leading the women's equivalent.
Benoit Huot and Daniel Dias led the way in the SM10 200m individual medley and the 50m freestyle respectively.
Britain's Nyree Kindred set a new Paralympic mark of 1:27.96 in the S6 100m backstroke with Australian Jacqueline Freney's 1:23.34 in the S7 class also a Games record as well as an Oceania mark.
Natalia Prologaieva was quickest into the S5 50m freestyle.