Jazz Carlin also claimed 400m freestyle silver as Britain, despite being in heavy training for the Rio 2016 Olympic Games, finished the competition in London with an impressive 22 medals.
The penultimate swim of the event saw O’Connor team up with Kathleen Dawson, Chloe Tutton and Francesca Halsall (pictured) to win 4x100m medley relay gold in a time of 3:58.57.
“It was absolutely amazing to win that on the final night,” said O’Connor, who trains with the British Swimming National Centre Bath in the London 2012 Legacy Pool.
“The crowds have been amazing all week and having that home support has really made a difference to our performances, so thanks to everyone.”
Walker-Hebborn – who had won mixed medley relay gold with O’Connor on Tuesday – then helped to conclude the championships in style as he, Adam Peaty, James Guy and Duncan Scott won the men’s 4x100m medley relay title in 3:32.15.
“To swim like that with these guys was incredible,” said Walker-Hebborn. “We’re not shaven down or tapered coming into this meet, so that just demonstrates to the rest of Europe and the World the position Great Britain are in.”
Carlin won a hard-fought battle to secure second place in the women’s 400m freestyle in 4:04.85, adding to her silver in the 800m race.
She was third-fastest after the heats and said: “I was a bit nervous after this morning but I just stuck to my race plan and it paid off. A silver is a good result and great motivation for me going forward.
“There are things I want to work on and fine tune with my coach as we really start to work towards Rio now, and this gives me a good platform on which to build.”