Laura Stephens struck gold with her first World Championship medal while the Women's 4x200m Freestyle Relay team clinched a brilliant silver on a memorable night five of swimming in Doha.
Stephens led from start to finish of the formidable 200m Butterfly event, putting together a brilliantly-paced race that ensured she had enough of a lead to hold on to in the closing 15m, ultimately out-touching the chasing Helena Bach of Denmark by less than a tenth of a second.
The result ensured Britain's first individual World Championship gold in a women's event since Rebecca Adlington's victory in the 800m Freestyle in Shanghai in 2011.
"I'm definitely very happy, it's really hard to put into words to be honest with you, I just can't believe it!" said Laura.
"I came into this meet hoping for three solid swims, to learn through the process - and to come away on top of the podium is kind of crazy.
"I had no expectations in terms of time, it's February, so I couldn't even come into this hoping for PBs or things like that. But that is a really solid swim, it's a great way to start off the long-course season and hopefully I can just get faster and faster.
"This definitely gives me a lot of confidence towards Paris. If anything, it just makes me more excited to get back into the hard work, into the training and to keep on improving."
Laura's golden success was followed later in the evening by silver for the quartet of Freya Colbert, Abbie Wood, Lucy Hope and Medi Harris in the 4x200m Freestyle Relay, a superb combined swim seeing this relay team - which was unchanged from the morning's heats - on to a podium after several recent near misses at global level - and firmly rubber-stamping its place at Paris 2024.
Colbert's strong opening 100m laid the foundations for impressive swims across the foursome, with the surging final 50m of Wood's leg moving them through from fourth to first at halfway.
With a medal well up for grabs, Hope and Harris kept their composure across their efforts as China began to pull clear, Harris anchoring the quartet to get her hand on the wall for third.
After an agonising fourth in Fukuoka last year, this was a hugely satisfying result that will give the Women's 4x200m Freestyle Relay group even more momentum on the Olympic run-in.
"I think the disappointment of coming fourth at Worlds last year was the first time you could really tell the girls were actually gutted, and that we were taking it a lot more seriously," said Abbie afterwards.
"We have such a strong five girls, including Freya Anderson, that we can swap in and out. Getting a silver here without one of our best freestylers is just so exciting for Paris, and I think everyone is happy with their swims as well.
"I think we really surprised ourselves tonight, especially because it's quite hard here doing this as our first long-course meet of the season, where we are against girls that are tapered and targeting this meet.
"We handled ourselves really well, we were all in a really good mood today and were just really happy going into the race - and I think that really reflected in our swimming."
On top of the two Thursday medals for Britain, there were a couple of close fourth places for Lauren Cox and Matt Richards, in the Women's 50m Backstroke and Men's 100m Freestyle.
Both missed the podium by 0.04s on the touch, although both performances bode well for where the swimmers are at this stage of the season, with the British Swimming Championships on the horizon in early April. Cox showed good swimming speed in her race, as she did across the 100m event, while Richards - racing from an outside lane - was strong in the closing stages to very nearly break into the medals.
Duncan Scott was sixth in the Men's 200m Individual Medley final as his busy week of top-level racing continued in the other GB final involvement of the evening.
In semi-final action, Anna Hopkin's impressive meet saw her qualify third-fastest for the Women's 100m Freestyle showpiece, but Luke Greenbank and Brodie Williams just missed out on the final of the Men's 200m Backstroke.