Sian O'Callaghan, 22, from Swindon
She is described as white, 5ft 3in tall,
of medium build with brown, straight hair
and green eyes.
last seen wearing a black bolero-style jacket
over her grey dress and flat boots. She was carrying a
dark handbag which had a beige flower attached.
Here is all the information as events unfold.
Latest update 27 March, 11:30
Fri 18 March
Sian O'Callaghan was last seen leaving Suju nightclub in Old Town in the early hours of Saturday morning (of 19 March). She had also visited Long’s Bar in Victoria Road earlier that evening.
Sat 19 March
She was out with girl-friends. She told one friend that she would see her on the dancefloor in "ten to 15 minutes" once she had finished chatting to another girl outside. But CCTV shows her leaving a toilet, walking down the stairs, out the front of the building , then along the High Street at 2:52am, No-one has seen or heard from her since leaving the nightclub.
Her partner (Kevin Reape, 25) said he woke to discover she had not returned to their Westmorland Road flat, so he sent her a text message "I'm worried" at 3.24 but received no reply.
Mobile phone records show that when her phone (a LG E900 Optimus mobile phone) was 12 miles away in the Savernake Forest when it received the message.
The alarm was raised at 9.45am on Saturday morning when she had not returned home. Wiltshire Police start an investation.
Mon 21 March
Wiltshire Police with members of the public are searching 4,500-acre area for any signs.
Chief Inspector Mike Jones of Wiltshire Police said: "Sian doesn't appear to have any reason in her personal life that would indicate that she might want to leave the area."
An anonymous donor has offered a £20,000 reward to find missing Swindon nightclubber Sian O'Callaghan.
Appealed for information to help find her at a (3pm) news conference were Miss O'Callaghan's parents Mick, 51, and Elaine, 48, her younger sister Lora, 19. brother Liam, 24, and her partner Kevin Reape, 25
Tue 22 March
More than 20,000 people have joined an online social networking group to offer support, along with thousands of messages on twitter.
A Kathy Davies (of Underdown Close, in Wanborough) booked two free coaches to travel to Savernake Forest at 2:30pm. "I’m just like everyone else in Swindon: passionate about finding Sian", she said. But over 100 people gathered in Commercial Road to board them. Several hundred volunteers are now at Savernake trying to help, but there are too many people for the police to deal with, and have turn some away.
Posters have been put up all around Old Town by Sian's friends.
Wed 23 March
The police now have slightly better data on the phone location, which rules out some of the seach area. More than 60 dedicated officers are conducting enquiries into her disappearance.
Teams of specialist officers, police dogs and 34 volunteers of Wiltshire Search and Rescue (Wilsar) continue to search the area. Several hundred volunteers meet at Postern Hill, in Savernake Forest at 10.30am to help. Coaches are arrange to bring members of the public to the location. People were being asked to sign in on arrival and be briefed on the operation and only search where they were told to.
"We have not found anything significant...", says Swindon Police divisional commander.
In Gorse Hill, St Barnabas Churc , A vigil and prayer service was held at 9pm. About 200 people of all ages came together for the service and worshippers came to light candles and say private prayers.
The reward has been doubled to £40,000
Thur 24 March
Police process CCTV from the high street that shows a green taxi turning around to pick up Sian.
At 12:30pm, Chris Halliwell, 47, a divorced father-of-three teenage girls, was arrested on suspicion of the kidnap, and two murders.
Det Supt Steve Fulcher said at a 5pm news conference,"The location of two bodies have been identified to me by this individual, one of whom has yet to be identified formally, but I am quite clear is Sian.
"I have informed Sian's family, who are obviously deeply distressed."
The man was stopped while parked in a taxi waiting area at the ASDA Wal-Mart supermarket in north Swindon. Eight police cars had surrounded his green Toyota Avensis estate.
Forensic officers searched his house at 12 Ashbury Avenue, inside and the outside of the property. A number of items are being brought out and put into a police van.
Sian was found at Letcombe Regis, some seven miles east of Swindon, close to the Uffington White Horse, Oxfordshire. An area of the road and the verge has been sealed-off and is being guarded by a number of police officers.
Floral tributes, messages, teddy bears and a large number of scented candles have been left in front of the club by mourners.
Fri 25 March
The police are searching Northleach/Eastleach in Gloucestershire for a body of another person who went missing from Wiltshire "several years ago".
Other locations are also being searched, including Ashbury village.
Police said, "I believe that Sian's body was moved to the Uffington area by this individual... Sian's body has now been recovered.. Post-mortem examinations are ongoing on Miss O'Callaghan's body,"
Sat 26 March
A body has now been found at the second location which was pointed out by Mr Halliwell. Its believed to be of a woman abducted in Swindon between 2003 and 2005, but yet to be identify.
Sian's body has been identified by her family. This was revealed today by Detective Superintendent Steve Fulcher, who also told the press conference that there was no indication she was sexually assaulted.
At 8pm, thousands of people gathered at the town's Polo Ground for a two-minute silence, where hundreds of lantern's were sent flying in to the nights sky. They could be seen for several miles across Swindon.
Sun 27 March
Mr Halliwell has been charged with Sian's murder, and is due to appear before Swindon magistrates on Monday.
Mr Halliwell remains in police custody at Gablecross Police Station in Swindon.
Police are still digging on Baxter's Farm, in the Gloucestershire Cotswolds.
. . . . . . .
Police are currently appealing for information about items believed to have been in Miss O'Callaghan's handbag. The bag is described as large and dark, with a beige flower on the side.
Items within the bag would likely be a front door key with a "distinctive pattern", a black car key with yellow insulation tape, a Tesco Clubcard key fob, lip gloss and a yellow Kinder Egg plastic casing containing an orangey-brown squirrel with a felt belly.Events..
20.03.11 18:00 Facebook page : Help Find Sian O'Callaghan
20.03.11 18:21 BBC News : Missing Swindon woman last seen leaving nightclub
21.03.11 08:52 Advertiser : Hunt goes on for Sian
21.03.11 09:55 Advertiser : Concern after woman disappears leaving nightclub
21.03.11 10:54 Advertiser : Did you see cars in Savernake Forest
21.03.11 11:00 Guardian : Police search for missing woman last seen in Swindon nightclub
21.03.11 11:26 Advertiser : Police set up mobile unit
21.03.11 12:08 Advertiser : Police search the Lawns
21.03.11 15:39 Advertiser : Boyfriend gives emotional plea to find Sian
21.03.11 16:17 This is Wiltshire : Boyfriend's plea over missing nightclub girl
21.03.11 16:25 Sky News : Appeal For Help To Find Missing Swindon Woman
21.03.11 17:06 BBC News : Sian O'Callaghan's boyfriend makes emotional appeal
21.03.11 17:09 Mail Online : Boyfriend and hundreds of friends of missing club girl Sian join huge police search
21.03.11 18:12 The Sun : Sian O'Callaghan seen on CCTV
21.03.11 19:22 BBC News : Boyfriend's appeal for missing Swindon..
21.03.11 20:00 Facebook : Help Find Sian O'Callaghan : CCTV Video released
21.03.11 20:00 ForEverSearching.com : Sian O’Callaghan
21.03.11 21:25 Daily Mail : Last known movements of missing Sian O'Callaghan captured on CCTV
21.03.11 23:00 Small World : Sian O’Callaghan’s family breaks down
21.03.11 23:00 Metro : Sian O'Callaghan's boyfriend: Someone must know where she is
21.03.11 23:00 The Mirror : Police search woods for missing PA Sian O'Callaghan
21.03.11 23:00 Channel 4 : Police search Wiltshire forest for missing Sian O'Callaghan
21.03.11 23:00 The Independent : Boyfriend appeal for missing clubber
22.03.11 00:00 The Sun : Please find Sian, begs boyfriend
22.03.11 08:55 Advertiser : MISSING WOMAN: Family appeals for information
22.03.11 10:12 Advertiser : MISSING WOMAN: Appeal for CCTV footage
22.03.11 10:20 Advertiser : MISSING WOMAN: Friends and colleagues pull together
22.03.11 10:37 Advertiser : MISSING WOMAN: You can help search forest
22.03.11 10.40 Advertiser : MISSING WOMAN: Suju is at centre of investigation
22.03.11 11:10 Advertiser : MISSING WOMAN: Police scouring area
22.03.11 13:43 Advertiser : MISSING WOMAN: £20,000 reward for information on Sian
22.03.11 16:16 Advertiser : MISSING WOMAN: Public asked to hold off forest search
22.03.11 16:55 ITV : £20,000 missing reward
22.03.11 17:29 ITN : Hunt continues for missing clubber
22.03.11 19:02 Advertiser : MISSING WOMAN: Volunteers needed to help with search again
22.03.11 19:18 BBC News : Hundreds search forest for missing Sian O'Callaghan
22.03.11 19:02 Advertiser : MISSING WOMAN: Volunteers needed to help with search again
23.03.11 05:11 BBC News : Search for missing Sian O'Callaghan set to continue
23.03.11 08:30 Advertiser : MISSING WOMAN: Volunteers expected to join search again today
23.03.11 09:21 Advertiser : MISSING WOMAN: Detective says Sian investigation gathers pace
23.03.11 09:30 Advertiser : MISSING WOMAN: Volunteers expected to join search again today
23.03.11 09:30 Advertiser : MISSING WOMAN: Friends hand out posters in Old Town
23.03.11 10:10 Advertiser : MISSING WOMAN: 'My heart goes out to them all'
23.03.11 10:42 Advertiser : MISSING WOMAN: Elmina Road incident not linked to Sian disappearance
23.03.11 12:23 Advertiser : MISSING WOMAN: Police turn members of the public away from forest
23.03.11 12:53 SIAN O'CALLAGHAN: Man arrested on suspicion of kidnap
23.03.11 14:11 Advertiser : MISSING WOMAN: Police praise public and press
23.03.11 14:36 Advertiser : MISSING WOMAN: Chief Inspector - "Swindon is still safe"
23.03.11 19:55 ITN : Police "closing in"
23.03.11 20:11 ITV : Police: "Close to identifying Sian's whereabouts"
23.03.11 21:00 Facebook event : The vigil service and prayer for the safe return of Sian O'Callaghan
23.03.11 21:10 BBC News : Police 'very close' to finding missing Sian O'Callaghan
23.03.11 21:11 Advertiser : MISSING WOMAN: Police praise public and press
24.03.11 08:00 Advertiser : SIAN O'CALLAGHAN: Questions to the man leading the search for Sian
24.03.11 08:30 Advertiser : SIAN O'CALLAGHAN: Hotel does its bit to help
24.03.11 09:10 Advertiser : SIAN O'CALLAGHAN: Hundreds say a prayer for Sian
24.03.11 09:53 Advertiser : SIAN O'CALLAGHAN: T-shirts used to widen the appeal for news of Sian
24.03.11 09:56 Advertiser : SIAN O'CALLAGHAN: Police hunt for green car with taxi markings
24.03.11 10:06 Advertiser : SIAN O'CALLAGHAN: Family thanks public
24.03.11 10.18 Advertiser : SIAN O'CALLAGHAN: Teachers' concern for former student
24.03.11 10:48 Advertiser : SIAN O'CALLAGHAN: Police reveal Sian's handbag contents
24.03.11 11:04 Advertiser : SIAN O'CALLAGHAN: Reward for information now £40,000
24.03.11 12:11 Advertiser : SIAN O'CALLAGHAN: Police tow green taxi away from supermarket car park
24.03.11 16:32 BBC News : Sian O'Callaghan search: Kidnap arrest made in Swindon
24.03.11 16:32 Advertiser : SIAN O'CALLAGHAN: Officers search Swindon house
24.03.11 17:22 Advertiser : SIAN O'CALLAGHAN: Two bodies found
24.03.11 17:31 BBC News : Sian O'Callaghan search: Two bodies found
24.03.11 18:00 Facebook : R.I.P Sian O'callaghan
24.03.11 19:35 Yahoo : Two bodies found in search for Sian
24.03.11 20:24 Sian O'Callaghan found dead amid fears over second body
24.03.11 21:11 Daily Mail : Police hunting for 'kidnapped' Sian O'Callaghan find body by the famous White Horse of Uffington
25.03.11 08:29 Advertiser : SIAN O'CALLAGHAN: A town in shock
25.03.11 10:11 BBC News : Wiltshire Police search for a second body
25.03.11 10:26 BBC News : Sian O'Callaghan murder police search for second body
25.03.11 14:01 BBC News : Sian O'Callaghan: Police seek body of missing adult
25.03.11 14:35 Mirror : Sian O' Callaghan: 'Second victim' missing for years
25.03.11 14:57 Advertiser : SIAN O'CALLAGHAN: Police search field in Eastleach
25.03.11 15:12 BBC News : Sian O'Callaghan: Police seek body of missing adult
25.03.11 16:36 Advertiser : SIAN O'CALLAGHAN: Police continue hunt for second body
26.05.11 16:06 Evening Advertiser : SIAN O'CALLAGHAN: Family identify body as Sian
26.05.11.20:54 BBc News : Sian police find human remains in Gloucestershire
27.05.11 11:34 BBC News : Man charged with Sian O'Callaghan murder
Also worth seeing the police page.
BBC has now published a timeline