And Glasgow's Gregor Tait lowered his own British record to 1:51.66, as he finished sixth in the 200m backstroke.
It has been a highly successful event for the home swimmers, who have set 44 British records as well as nine Commonwealth and seven European benchmarks – with 18 world records being broken at the Manchester Evening News Arena.
The final session saw Davies take silver in the 1500metres freestyle, with the remaining quartet adding bronzes as the championships drew to a close. Davies was runner-up as Yuri Prilukov claimed his third consecutive world title in a race featuring the top four finishers at last year's World Championships.
Prilukov – who won world championship silver – touched in 14 minutes 22.98 seconds. Davies, the Olympic and world bronze medallist, finished in 14:36.30 – four seconds outside his own British record.
Davies has been in heavy training, preparing for the World Open Water Championships in Seville next month which act as qualifying for the inaugural Olympic 10 kilometre open water competition.
The 23-year-old was therefore ecstatic, saying: "I can't believe I just swam that time.
"I've been in heavy training since Eindhoven (European Championships) ready for Seville for the open water – which is very important to me.
"I didn't want to pull out of this event though – and I'm glad I came here.
"At the end I was absolutely done in. I used all the guts in me.
"(If you had told me before) I would have taken it like a shot. I have been really struggling in training – I thought I was going to be lapped."
Tancock entered the final session, having won a gold in the 100m backstroke in European and Commonwealth record time and silver in both the 50m backstroke and 200m individual medley in British record time. He returned for the 100m equivalent where he claimed his fourth medal, a bronze, and another national record of 52.21 – just touched out by Peter Mankoc, the Slovenian also eclipsing the European record Tancock set yesterday.
Tancock said: "It's a fantastic achievement. If someone had said to me I would have walked away with one medal I wouldn't have believed them. Now I have four of them. The crowd have been amazing. I hope there will be a few more Liam Tancock fans out there now."
It caps a remarkable fortnight for the triple world championship bronze medallist, who set a new world record in the 50m backstroke at the Olympic trials in Sheffield.
Halsall claimed her fourth medal with third in the 50m freestyle, lowering her personal best to 24.11 in a race which saw Marleen Veldhuis improve her own world record to 23.25. The Liverpool teenager finished in Manchester with one silver and three bronze medals – as well as turning 18 yesterday.
Halsall said: "If anyone had said I would have got one I would have taken it. To win four is a dream come true.
"It's the best and most memorable birthday I've ever had."
McClatchey, pictured, claimed her third medal when she was third in the 200m freestyle in 1:55.15.
The Loughborough student said: "I have never really been a short-course swimmer – so to get a bronze medal here is amazing."
Tait then lowered his own British record to 1:51.66, as he finished sixth in the 200m backstroke, which was won by Austrian Markus Rogan in a new world record time of 1:47.84.
Suzanne van Biljon, of South Africa, won the 200m breaststroke; Oleg Lisogor retained his 50m breaststroke title; Moss Burmester won the 200m butterfly, and Russia set a new world record in the 4x100m medley relay – in which Britain finished fifth.
Jemma Lowe lowered her own British record to finish third in the 100m butterfly in 56.84, with Felicity Galvez setting a new world record of 55.89. It was the second bronze of the meet for the 18-year-old, after her efforts with the 4x100m medley relay.
Nathan Adrian was the first champion of the evening when he claimed the 100m freestyle title in a championship record of 46.67.
Another world record fell in the next event when Sanja Jovanovic lowered her own mark to 26.37, with Lizzie Simmonds eighth in 27.29 before Rogan touched out Ryan Lochte.