Here is a timeline covering the period in which the body dismemberment and disposal must have taken place. It is based on testimony given so far. Largely taken from UK & Eire site. I have changed names to initials.
Fri February 20: 12.20pm - NM buys two bottles of drain cleaner from the Rajani superstore in Bristol.
12.51pm - NM purchases a MacAllister circular power saw, face masks, gloves and goggles from B&Q in Horfield, Bristol.
2.18pm SH texts NM that memory cards and PS4 stickers have arrived
3.10pm - SH texts NM: 'What time do you finish work LOL? Hugs and kisses'.
4pm - Becky's father reports the teenager missing to police.
5:30pm SH puts message on FB Hi, can you keep an eye out for Becky Watts and if you see her message me because she is missing.
6.25pm - Police arrive at Becky's home and speak to Mr and Mrs G, NM and SH. The couple claim they heard Becky leave the previous morning.
8.45pm - A Chinese takeaway is ordered to Cotton Mill Lane.
9pm - A device of NM and SH searches 'Do you want to hide a body?' on YouTube.
Sat February 21: NM and SH go to Asda in Bedminster and buy black bags, rubble sacks, rubber gloves, bleach and three rolls of cling film. They purchase £20 of electricity from a local shop.
Sun February 22: NM and SH buy black rubble sacks, tape and a sponge from a 99p store and a Wilko at the Broadmead shopping centre in Bristol city centre, then tape and cling film at Sainsbury's in Brislington.
Mon February 23: Police attempt to enter Cotton Mill Lane but no one answers the door.
4.38pm - A mobile phone belonging to SH and NM searches for 'Find Becky Watts' on Google.
4.40pm - SH rings her estranged mother, LD, and stepfather KS and arranges to visit their home in Wilton Close, Southmead, arriving about 30-40 minutes after the call.
6pm - Detectives return to Cotton Mill Lane but NM and SH are not at home. They speak to the pair at Wilton Close.
SH agrees police can search their home the following day.
Tues February 24: NM/SH leave Wilton Close in the early hours and were given a lift home by a friend.
In the early hours, KD and JI borrow a van from their work in Filton.
1.10am KD got a message from JP saying: "Ah ok you going to hide it for him? We could do with the money. lol. xxxx."
1.18am JP sent another which said: "Cool, that's a deposit on the house. lol."
2.19am - CCTV shows a van moving between Cotton Mill Lane and Barton Court, with light coming on by the garden shed.
2.31am - The white van is seen heading back towards JI and KD's work in Filton
9:36am NM texts AG saying "Hi, just thought I would update you, police have searched S's house and obviously found nothing. Hope you are all managing as best as possible, I will see you tomorrow."