Oliver Hynd became Paralympic champion in the SM8 200 metres individual medley with an unstoppable performance at the Aquatics Centre.
The 17-year-old has enjoyed a superb Paralympic debut and came into the race with a silver and bronze already from the meet.
Fourth after the opening butterfly leg, Hynd moved through the field on the backstroke to turn second at halfway. The Nova Centurion swimmer had moved into first with 50m to go and his opponents made no headway as the Briton clocked two minutes 24.63 seconds for victory. Brother Sam was just out of the medals in fourth.
Hynd was stunned by his gold and told Channel 4: "I don't believe it - it's amazing. When I touched I didn't really want to believe it. I thought 'it can't be right' but I'm Paralympic champion and I'm over the moon. This has just been amazing."
Robert Welbourn claimed Britain's third medal of the night with a valiant bronze in the 400m freestyle.
The Chesterfield-born swimmer went into the final ranked fifth after a heat that promised a highly-competitive race with little more than six seconds separating the field.
Welbourn, who trains in Swansea under Bud McAllister, was first at the 250m mark before being overhauled by eventual winner Ian Jaryd Silverman.
Second with 50m to go Benoit Huot edged ahead of the Briton with Welbourn touching in 4:18.18
Hannah Russell won Great Britain's fourth medal of the night, and her third of the meet, when she was third in the S12 100m backstroke.
Charlotte Henshaw missed out on gold by just three hundredths of a second in the SB6 100m breaststroke with team-mate Liz Johnson taking bronze and Louise Watkin rounded off the medals for Britain with silver in the S9 50m freestyle.