BBC SPORT | Athletics | World Champs day nine as it happened
Christine Ohuruogu, Marilyn Okoro, Lee McConnell and Nicola Sanders hung on behind the USA and Jamaica in a UK record of three minutes, 20.04 seconds.
As predicted, the USA wrap up the men's 4x400m with ease from the Bahamas and Poland as Britain come home in sixth.
Bernard Lagat took the 5,000m gold to add to his 1500m title while Britain's Mo Farah finished a creditable sixth.
ACTION AS IT HAPPENED (ALL TIMES BST):
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1322: That is it for the live now from Osaka. The USA topped the medal table with a total of 26 medals - 14 of them gold - from Kenya and Russia. Great Britain finished 10th in the medal table with five - which was above the required target of five. And now can we improve on that at the Beijing Olympic next year. Until then . .
1301: That's it for the medals in Japan and here's a word from the British quartet who claimed the fifth and final medal for the squad.
Christine Ohuruogu first up says: "We are just happy with our medal and it's a national record too, so it's a good achievement."
Nicola Sanders: The girls did brilliantly to keep me in reach of a medal. I knew the Russian anchor tired in the individual race and that I could get a medal. We did something special."
1252: A faller impedes the British squad and Richard Buck is now miles behind as Williamson passes on to Jeremy Wariner, who will lead the US home.
1250: Steele does well as he hands on the baton to Rob Tobin, who will break with the field which is already being led way, way ahead by Angelo Taylor.
1249: The men's 4x400m relay is about to start and we haven't even had time to run through the British team. UK champion Andrew Steele goes first for Brits while Lashawn Merritt leads off the red-hot Americans.
1247: Favourite Blanka Vlasic of Croatia takes the high jump gold after clearing 2.05m while Russian Anna Chicherova and Italian Antonietta Di Martina, who both went over at 2.03m, share silver.
1244: Tero Pitkamaki had already won the javelin title with his second attempt of 89.16m but he does even better with the pressure off on his sixth throw. The Finn launches the javelin and then falls flat on his face, but the spear flies out to 90.33m. He has the gold from Andreas Thorkildsen and American Breaux Greer.
1237: It's the USA, Jamaica, Russia and Britain - McConnell tries to close it up and leave Sanders to battle it out.
1236: Allyson Felix stretches away the lead for the American but Britain are in fourth as Okoro hands off to McConnell.
1235: Ohuruogu is going well down the back straight and she looks as though she has ran a storming 250m but Britain comes through in second behind Jamaica.
1232: Ohuruogu sits on her blocks, as she aims to finish her championships with a second medal.
1225: Five minutes to the women's 4x400m final and Christine Ohuruogu returns to the British squad and will start things off with 800m runner Marilyn Okoro on the second leg, Lee McConnell third and Nicola Sanders on the anchor.
1223: The javelin final is into the final throws. Pitkamaki still leads, from Andreas Thorkildsen while American Breaux Greer has climbed up to bronze.
1220: The women's high jump is shaping up nicely with three over at 2.03. And those three are Croatia's Blanka Vlasic, Russia's Anna Chicherova - who sets a personal best - and Italian Antonietta di Martino.
1212: Russia's Yelena Soboleva leads a pack of six athletes with two laps to go in the 1500m.
1209: Five women are over 2.00m in the high jump final while out on the track we're almost ready for the 1500m.
1204: Let's catch up with Mo Farah, after his sixth-place 5,000m finish. He tells BBC Sport: "I'm definitely disappointed with that but it's my first world championships and I hope to learn from that. My legs just went in the last 50m but now I want to go to the Beijing Olympics and see what happens."
1155: The finals are coming faster now, as the men's 800m goes under the gun in Japan. Canada's Gary Reed leads at the bell but the race is very, very open indeed.
1153: Swedish defending champion Kajsa Bergqvist goes out of the high jump as she fails all three attempts to clear 1.97m.
1145: Farah gets overtaken on the back straight, but it was a brave move from the Briton.
The field kick away and the race descends into a sprint for the line between Lagat and Eliud Kipchoge. The Kenyan-born Lagat, who now runs for the USA, holds on to win in 13 minutes 45.87 seconds ahead of Kipchoge and Moses Ndiema Kipsiro. Farah comes home in a creditable sixth. So that's the 1500m and 5,000m titles for Lagat.
BBC commentator Steve Cram
1143: Farah takes to the front with 500m to go, it's a bit of a long way out to kick for home but let's see.
1140: Four laps to go and Farah is in amongst in, nestled in the front four. The pace has slowed again which could play into Lagat's hands who will have a bigger sprint final. Farah gets a knock from behind on that lap, but recovers after a stumble.
1136: Benjamin Limo ups the pace at the front of the 5k through the first 1,000m. Limo is the defending champion and named his son Helsinki after claiming victory in the Finnish capital in 2005. It could have been worse for Limo Jr, as he was originally called Tony.
1132: The runners are off around the 12-and-a-half laps in temperatures of 30C. It is a slow pace so far. In the midst of all this, the men's javelin final is now into the second round. Finland's Tero Pitkamaki has the lead after hurling 89.16m.
1128: The athletes are being introduced ahead of the men's 5,000m and there is a big, big smile from Farah. American 1500m champion Bernard Lagat is tipped to finish the race with a winning smile though. We shall see.
1125: "A medal seems a bit beyond Mo Farah in the 5,000m, as he's hardly run, but his training regime and the fact he lives, eats and trains with top African Athletes will hold him in good stead for a top 8 finish at least and maybe a PB?"
Droitrob on 606
1116: It's a Sunday so you may have stayed in bed and read the papers, and so you may not know that the first gold of the final day went to Catherine Ndereba in the marathon. Japan's Reiko Tosa collected Japan's first medal of the championships, hanging on to bronze. Tosa looked beat by the end of it, running with her arms loose and jaw gaping, grimacing over the line. Britain's Mara Yamauchi came ninth.
1105: So we're all set for another day and things are already under way in the women's high jump. Croatia's Blanka Vlasic has the world-leading height of 2.07m this season but Swede Kajsa Bergqvist is out to defend her title. The bar has been raised to 1.94m so far.
1100: The time is almost upon us to say sayonara to the world championships BUT first there is the final day of action at the Nagai stadium - and it should be a cracker.
The men's 4x400m relay brings the curtain down and with 400m medallists Jeremy Wariner, LaShawn Merritt and Angelo Taylor running for the US it looks like they'll have the gold sewn up.
Britain's Andrew Steele, Rob Tobin, Richard Buck and Martyn Rooney are also in the final - though Tim Benjamin seems unlikely to shake off a virus in time to join the squad.
But forget the men. It's the women's race where things could get interesting.
400m champion Christine Ohuruogu is back to liven things up for Britain along with silver medallist Nicola Sanders, Lee McConnell and either Donna Fraser or Marilyn Okoro.
The rumour is that the world's fastest 400m runner Sanya Richards will not return to the US quartet - and that could well play into Britain's hands.
We've also got the women's high jump, 1500m and the men's 5,000m, 800m and javelin to decide.
You weren't thinking of going anywhere now where you? Good.