Josef Craig was staggered to have defied his tender years as he set a new world record in the S7 400 metres freestyle as ParalympicsGB continued to sizzle in the pool.
The 15-year-old cut his own best by nine seconds as he hurled down a marker on Thursday morning in four minutes 45.79 seconds.
The South Shields-born teenager's time saw him dip 1.37secs inside team-mate Jonathan Fox's world record set at last year's European Championships in Berlin.
Craig was completely taken aback and said: "I thought 'God I've just done a massive PB, that will be my achievements done for this competition' but then I got my focus back and saw it was a world record next to the time and I just thought there's a problem with the clock here.
"I can't break a world record yet, I'm still 15, just take it one step at a time but I just don't know what to say about that, it's just amazing."
Craig added: "I've been training really hard but I never thought there would be a world record time in there but it just goes to show what amazing help I've got up at Manchester."
Fox was second fastest through in 4mins 49.91secs with the possibility of two Britons on the podium tonight a very real prospect.
The 21-year-old won the S7 100m backstroke on the opening night but since then has not made the top three in his 50m and 100m freestyle races.
He was magnanimous about his younger team-mate wresting his world record and said: "Josef is 15 and has been training really well and hats off to him for breaking it.
"I am a good team player, I take a defeat when I get one and we'll see - I'll come back fighting tonight and hopefully there will be two Britons on the podium so we'll see what happens."