Overstepping Colleague what to do?

[WiseAdviceNeededPlease]

Started my job 6 months ago, I'm part of a small management team. Unfortunately my male colleague who has been at the company longer seems to be competing with me instead of wanting to collaborate. He very publicly announced a decision to hire a candidate that he liked over one that I felt was a better fit when the decision should have been mine and he knew my thoughts on it, I was the hiring manager so it made no sense for him to overrule me. He's done this twice. We're supposed to be working together so this makes our team look bad. I have told him how I feel about it in various different ways but he isn't interested. I'm in a difficult position as he has a lot of information I need to know because I'm new and is already reluctant to share so if I complain about him things could get worse. The other issues is that he works at the office where all the upper management are based whereas I am pretty much solo in my location. I'm going to talk to my boss (also male) about it tomorrow he is nice but very passive and this other guy dominates all the group conversations. It's hard because I really need to find a way to get along with the colleague as it's essential we work well together but the more I get to know him the less I like him. He is charming and lively but seems to be very self centered and egotistical He needs a lot of attention and air time. He is very keen to secure his own position and not interested in supporting me to set me up to succeed. I work in a male dominated industry, I'm not sure if my boss is really interested in standing up to this guy I think he just wants a quiet life. Any advice?

Are you sure you judged the hiring decision correctly? If you're working alone and also need lots of information from him as you're so new, making he does have a better grasp of what is required from the role?

In the first case his hiring decision was eventually rejected by another higher up stakeholder who saw the same problems I did, so I think my choice which we landed on in the end was better. The second situation is less clear, (it's the same candidate he wanted to hire for the first role) that he's created a role for and he cut me out of the conversations after I voiced reservations the first time round so it's harder to judge. I've also inherited two problem employees he hired before I joined the company which makes me question his judgement. One of these people (who I'm now performance managing) is someone he was warned not to hire by three experts but he did it anyway. He has made some very good hires also but he seems a bit reckless and unwilling to listen to other's opinions. I don't feel I can trust him to have my back so I'm not sure how I can fix that.

He does sound like a loose cannon who occasionally strikes gold and is willing to back himself on doing it again. And then the ones that aren't so good become someone else's problem...
If his main role is hiring and creating jobs I'm not sure there is much you can do. If he's poking his nose into departments that aren't his however you might be able to do a bit more and create email trails for every decision so he can't cut you out. I think you can forget about him being a team player or having your back - work with his good points and always be aware of his limitations and guard against damage caused by them.

Thank you @Finsburyfancy this is very helpful advice, idealistically I was trying to think of a way to be able to trust him but that is not very realistic since he's out for number 1 and sees me as competition. Hiring is just a small part of our roles, we have the same job title. I'm not even sure if it's worth mentioning this behaviour to my boss as they work together in the same country and recently attended a "summit" together for our team in a different country which I was not notified about or invited to... I just don't think I'm fully on his radar and the colleague who is very ambitious is taking advantage of this. My morale has plummeted,

Update to say that my Boss said he was "surprised" to hear that the colleague had taken over my hiring process which to me sounds a bit like he doesn't believe me. I said I was surprised too. He also said that colleague is very attached to that team which I guess is his way of excusing him elbowing out of the way. He confirmed that I am the same level in the hierarchy as my colleague so he wouldn't expect me to defer to him automatically. He also apologized for not inviting me to the "summit", he said it was booked very last minute (for himself and the two other male colleagues in his team) and said he would invite me next time... Not sure I want to go now, I think I'm spoiling their boy's club.

Not sure how to work with this group? He also offered to meet with me weekly instead of every 3 weeks. He said "We threw you in to see if you could swim" which to me sounds as if he's saying I'm not coping rather than admitting they are cutting me out and not sharing info. I think he felt criticized and didn't like that. I was very polite but said I understand that budgets can be tight but maybe next time I could join by zoom so I have a "seat at the table and can represent my location." Had to say something or I will feel like a total doormat.

Oh this sounds really hard work. I agree that it's a boys club and they don't want you rocking the boat or ruining their echo chamber of opinions. Unfortunately I don't think you'll get much credit for work here, and it might turn out to be a pretty toxic environment, so if you do decide it's not for you I would try to not let it affect your confidence. Regarding working, I think I'd just remain polite, get the work done to a high standard, and use the evidence of my own competence to do the talking for me. Doesn't sound like you'll be able to persuade them that this guy is a pain in the ass, but you should be able to demonstrate that you can't be steamrolled and that any push back you get from them is unfounded as you are strong at your job.

It does sound a bit like you are not coping, if after six months in the role you still need information / help from your colleague. Look at what you can do to improve your knowledge. Is it possible for you to go into the main office once a week?

This sounds like a horrendously toxic work environment. I would be looking for another job.

You need to challenge the colleague loudly and publicly. It will improve both his and other people’s respect for you, even if it makes him more difficult at the same time.

So, for example, if he sends an email about a hiring for your team you should reply with “Please retract this email Fred. I haven’t made a final decision about hiring for this role yet and, whilst I value your opinion, this isn’t the best fit candidate for my team.”

We're working on a massive project that's constantly changing so sharing information is vital, the rest of the team (the men who went on the trip) are all in one location and I am solo in another so I need them to share updates. Our team is part of a larger management group, I got the highest results in the manager's survey that was done last month across the whole (wider) team which my boss mentioned to me so he can't reasonably say I'm struggling. I found the comment "we threw you in to see if you could swim" quite offensive as I obviously can "swim" with minimal support. It was so bizarre seeing him all happy when he came back from the trip saying how great it was meeting the other team and building new relationships etc.. it was clear it hadn't occurred to him for a full week that they had excluded me. I'm disappointed as he had seemed to be more supportive and sensitive but I think he is heavily invested in the status quo and happy to use me as a work horse and let the boys have the majority of the perks. This is quite a typical experience for me (working in a male dominated industry) but I am very Senior now so it sucks to be still dealing with this...

I appreciate the advice but I'm not sure this will work as I have done this once now and brought the issue to my boss who seems to not want to engage with it just saying that he's "surprised" to hear this guy would do something like that and making excuses for why he would do it. I will still continue to be professional and assertive where needed but I'm pretty sure doing this had just made them close ranks against me.