The timeline released by counter-terrorism police detailing some of the movements of the novichok suspects around Salisbury on the day Sergei Skripal and his daughter, Yulia, were poisoned answers some questions but raises many more.

What do we know of the suspects’ movements before the attack?

The pair arrived at Salisbury railway station at 11.48am on Sunday 4 March. They turned left out of the station and walked directly to the residential area north-west of the city where Sergei Skripal lived. The pair were caught at 11.58am by a CCTV camera at a Shell petrol station on Wilton Road. On the opposite side of the road is a tree-lined path that leads to Montgomery Gardens and Christie Miller Road, where Skripal lived. If they went straight to the house and carried out the attack, they would have been at the Skripal front door shortly after noon.

Where were the Skripals at this time?

Sergei Skripal’s BMW was seen out and about in the city at about 9.15am on the Sunday. It was spotted heading from the area where he lived towards the city again at 1.30pm and Sergei and Yulia arrived at the Maltings car park in the city centre at 1.40pm. It may be that when the suspects applied novichok to his front door, he and Yulia were at home.

Where did the suspects go after allegedly sabotaging the Skripal front door?

They certainly did not return directly to the station. About an hour after the attack, at 1.05pm, they were in the city centre on Fisherton Street. The police have not given details of how they got there. They could have got there by retracing their steps back past the station and on into the city. Or they might have taken a less obvious route that involves walking alongside a riverside path known to have been frequented by Charlie Rowley, who was poisoned having found a bottle containing novichok at the end of June. There is another 42-minute gap in the timeline the police provided between when the pair were seen in Fisherton Street and when CCTV footage picked them up at the station. The suspects are not likely to have been walking around randomly – after all the police have said they carried out a reconnaissance mission the day before.

Did the suspects dump the fake perfume bottle containing novichok during one of the gaps in the chronology?

The police said they did not know where the suspects disposed of the novichok that they allegedly used to sabotage the Skripal door. Charlie Rowley has claimed he found a bottle containing novichok in a bin behind a charity shop in the city centre on Wednesday 27 June. But this account has to be treated with caution. He did not initially tell police about the bin. It was only after he spoke to ITV News about the bin that police sealed the area off and took it away. Rowley told ITV: “It’s a possibility that I may have found it here. I don’t know, all I can say is a vague description of an area and this being one of them.” It is entirely possible that he found the bottle somewhere else, perhaps on the riverside pathhe is known to have frequented.

Could there be two containers of novichok? Might there still be novichok in Salisbury?

Yes. Police said they could not say if the container used to convey the novichok to the Skripal door was the same vessel Rowley found. They added: “Despite the meticulous and painstaking searches, and although unlikely, it is impossible to guarantee that there are no other materials present in the Salisbury area.”

However, the police have now said they are confident the two poisonings in March and June are linked.