Inside the house party Jack O'Sullivan went to on the night he disappeared: Student wanted to make friends... but had an 'altercation' with a stranger and fell down the stairs before going missing, mo

The mother of missing student Jack O'Sullivan has today revealed how police failed to investigate that her son had fallen down the stairs and hit his head before getting into an 'altercation' at a house party on the night he went missing.

Catherine O'Sullivan, whose 23-year-old son Jack vanished after a party in the Hotwells area of Bristol on March 2, has been forced to hire a private investigator to find out more crucial details about the student's mystery disappearance.

Jack was unsure about going to the party because he barely knew anyone there, but his mother had encouraged him to go and meet new people as his friends from home had moved away.

He took the bus from his house in Flax Bourton to Bristol city centre to have drinks with three of his university friends at a Wetherspoons , before all four, two boys and two girls, ventured to a house party hosted by a girl on his law conversion course.

The University of Exeter graduate, who had moved back to Bristol for the law course, stuck with his group at the party on Hotwell Road, but at one point tumbled down the stairs and hit his head.

When a random partygoer joked about him having too much to drink, Jack shoved him in a brief clash, but this did not go further.

Jack texted his mum at 1.52am to say he was safe and planned to get a taxi and left the party an hour later, without saying goodbye to his female friend who was having a cigarette outside. He never returned home and has been missing for six months.

From having to trawl through CCTV and carry out searches herself to being denied access to crucial phone and Apple AirTag data, Jack's mother has become increasingly frustrated by Avon and Somerset Police's investigation.

And now, speaking to MailOnline about the latest revelations from the night of the party, Catherine said: 'It's been really sketchy.'

She explained: 'I immediately asked the police if they had spoken to people and they they said, 'Oh yes, we've spoken to people at the party'. But we have had conflicting reports.

'The girl at the party who was on the phone to him [later at 3.24am] said that Jack got into an altercation with someone as he was leaving the party.

'The police say they that it was nothing and that they haven't got any knowledge of that being any form of concern.

'We've tried to look into that ourselves with a private detective and he questioned some of the people. The interview with the boy that Jack had the description of an altercation with, his very descriptive interview says that he was standing at the bottom of the stairs as Jack was leaving.

'Jack tripped on the stairs and he laughed at him and said, 'You've had enough, mate', that type of thing. As Jack got up, he pushed him and that was the extent of the altercation.

'It was described as an altercation. Obviously we're not there so we have no idea. But what this chap went on to say was that Jack hit his head when he fell down the stairs.

'Now I went immediately back to the police with that and said you've never mentioned anything of the sort. [We asked] 'Can we look at the statements of the people at the party again?'

'But it was a slight fob off is the way I describe it, because the police read out some lines from their books. However, I don't believe that they were official statements. They said we've got nothing of the sort reported to us.

'We just can't get to the bottom of anything.

'When I recently asked again [for the party statements], they said they had told us what we needed to know and they couldn't officially give us these things to look at because it's a police investigation, and they're not allowed to share things of that nature.'

Catherine says she has been 'let down' by Avon and Somerset Police, leading to her hiring a private investigator and calling upon missing persons specialists in Northern Ireland and Scotland to help scour the near five-mile route he could have walked home along the busy A370 - something detectives have failed to do.

She told MailOnline that police officers were finally searching an area around half way back to their home earlier this week - after private specialist dogs had become 'agitated' in an 'area of interest'.

Catherine claims she had to wait a week for Avon and Somerset to 'consider' the report before they agreed to follow up and carry out searches on Thursday.

After Jack left the party at 2.57am, he walked south from the house along Christina Terrace and was caught on CCTV crossing the Junction Swing Bridge. This is only a short walk from the house, and Jack may have been walking towards a main road where he could more easily get a taxi.

At 3.13am, CCTV footage shows Jack walking under the Brunel Way flyover, having apparently walked there along Brunel Lock Road. This is a short, five minute walk along the northern edge of the Cumberland Basin.

The last confirmed sighting of Jack is at 3.13am as he walks onto a grassy area at the junction of Brunel Lock Way and Brunel Way, Bristol.

But while Catherine was forced to trawl through CCTV herself, she spotted a person - who she is adamant is her son - walking over Plimsol Bridge at around 3.25am, heading back in the direction of Bristol city centre.

When bungling officers were alerted to this, they later uncovered a second clip showing someone walking along the Bennett Way slip road at around 3.38am.

Jack attempted to call his female friend who was still at the party at 3.24am. When the friend called back 10 minutes later, Jack answered but only said 'hello' before the call cut off.

His phone remained active on Find My Friends until 6.44am, lasting pinging on Granby Hill, and Catherine could hear the phone ringing through when she was calling him, indicating the device was still working.

He also took an Apple AirTag out with him, which was attached to his keys, but the family have been unable to access the data on the tracking device due to privacy laws.

Speaking about the lead-up to the party, Catherine said: 'Jack only knew four or five people at the party.

'The rest were were unfamiliar to him. He would be meeting them for the first time. So I have been in contact with the girl that he knew the most.

'There's just blanks with everything, there's so many things that don't make sense here.

'The girl who hosted the party, it was her birthday, and she was one of Jack's fellow students on the law conversion course he was doing so she just invited a handful of people, and then her old university friends.

'Jack was in two minds whether to go because he didn't really know many people there.

'And I encouraged him and said, meet some new people because most of his school friends and university friends are dotted all over the country so he didn't have a sort of close body of friends living in Bristol.

'So I just thought it's an opportunity to meet new people.'

Catherine continued: 'What we know is that Jack called his friend, because by all accounts, what she tells us is, she was at the party with Jack. She went outside to have a cigarette but Jack stayed inside with the others.

'But when she got back inside Jack had gone and just left and she thought it was a bit strange that he'd left without saying goodbye which is a bit strange, because Jack isn't that sort of person really.

'So she went to look for him but she couldn't find him anywhere. And I think she started messaging him and said, 'Where are you?'

'He then rang her but she didn't answer the call. She said she had a problem with her phone, and she was trying to answer it, and it wouldn't connect.

'However, about 10 minutes or so later, she rang him back and she says he answered and just said 'Hello'.

'My question is, 'Was it Jack that answered?' But again, nobody can be accurate with that.

'She thinks it was Jack, but he just said 'Hello', and didn't say anything else. That was at 3.35am.

'Her account is that the phone line remained open for about 58 seconds. She didn't hear anything else in the background. She said she didn't hear vehicles or anything going past or a sound of any other person.

'And then the line cut out. All the calls she made after that were not answered.'

When asked if she wanted to speak further to the fellow revellers, Catherine replied: 'Well, not particularly because I think that if I hadn't seen Jack leave and I hadn't seen him walking, I would be more concerned.

'But I do think that quite a few people at the party weren't aware of him, because it appears that he wasn't in conversation with that many people there.

'He kind of stayed within the group of people he knew and I don't know if they would have any more information.

'They might recall him being there. Somebody might come out and say, 'Yeah there was a huge fight and this happened and that happened', but I would have expected that information to have been given to somebody along the way for consideration before now.

'So I don't think [they are] doing anything wrong, particularly. I mean, maybe they just don't want to get involved, or for them, it's not such a big deal. They're all budding lawyers, and maybe they just don't want the hassle.'

Jack's mother has called on the support of two charities based in Northern Ireland and Scotland to help search the route that Jack would have tried to walk home if this is what he tried to do.

Catherine revealed: 'They've been here on three separate occasions, but the main occasion they came was over a three-day period.

'They brought five dogs and 10 people and really scoured some of the areas that I've been questioning from the beginning of potential routes that Jack would have tried to walk home.

'Basically coming from Bristol towards the direction of where we live. Some of the areas are just not accessible by people. Some of it is not accessible even to the dogs.

'My main concern, literally from the first day was, could Jack have possibly tried to get home, tried to walk it. It's a four mile walk, but not insurmountable. It is something you could do.

'But part of it is really not safe, because there's a dual carriageway involved. And it's not very well lit at night.

'So we've asked repeatedly for the police to look at this area, but they refused. They said they had no reason to suggest that Jack had got that far based on his phone usage.

'But my argument was maybe he's not with his phone. Nevertheless, it was never done by the police.

'We just felt that it was an area of concern, given the fact that it can be quite treacherous.

'At the beginning we we were completely in the police's hands in terms of how they went about this, but as time's gone on, and you know some of the mistakes have been uncovered then you just think well, we we can't take anything for granted as being done very well.'

When trying to put the search area together, Catherine revealed that they asked police for the areas they had already searched - but they refused because it was an 'ongoing inquiry'.

'We're just trying to do everything that we possibly can to find him,' she said. 'It's not a competition of who actually does this, we just want to feel confident that everything is being done.'

Catherine has also revealed today how the family has instructed lawyers to apply for a court order to get Jack's phone data from mobile provider EE.

The police say they are unable to hand out the data without EE's permission, but EE say they can only give it out with the relevant authorities' permission.

'We're just going in a circle, back and forth. We're in the process of trying to get a court order to get the data released.

'I just want to be able to give it to somebody, a professional body that can analyse it and then tell me their findings so I can feel that that's been done properly.

'There are periods of data usage on that phone that the police have actually told us is factually correct.

'However, they can't then go to the next step of saying what that data is. They can say the size of it and they can say the times of it.

'We know that at 4.39am, the phone was using equivalent data to a nine minute video.

'We know that the messages I sent to that phone at 5.40am were received by that phone.

'And we know that the phone was still on the network up until 6.44am and then it stops.

'We've got all these kind of snippets of information, but they're not deep enough to confirm anything for certain.

'But speaking to technical people and various companies, they've said that they feel confident that they would be able to get more out of it than the basic stuff we've been told.

'We can't rely upon what we've been told by the police. We need to do it for ourselves.'

Catherine and her husband Alan previously told MailOnline that they feel they have been 'badly, badly let down' by Avon and Somerset Police and even lodged a formal complaint.

A spokesman for Avon and Somerset Police said: 'We are aware that Jack was involved in a verbal altercation at a house party in Hotwells the night he went missing and is reported to have fallen down the stairs.

'There is no evidence that Jack sustained a serious injury following this incident.'

Avon and Somerset Police say that since Jack's disappearance, more than 20 different teams and departments have been involved in the investigation.

They have been supported by other agencies and emergency services, such as the fire and ambulance service, National Police Air Service, and RNLI.

A spokesperson said more than 100 hours of CCTV have been reviewed, 200 hours of searches on the river and the surrounding banks, mounted police searches from Bristol city centre to Flax Bourton, 40 land searches, and 16 drone deployments.

The force said it has received almost 100 calls from the public with possible sightings, and eight media appeals have been issued.

Assistant Chief Constable Joanne Hall said: 'Our staff and officers remain committed to doing everything we can to find Jack and we do not underestimate what a distressing time this has been, and continues to be, for his family.

'When I look at missing persons investigations [in Avon and Somerset] over the last year, we've had around five and a half thousand.

'Missing people are somebody's loved ones, they're somebody's family, and we don't close the door on that.'