Messy situation, need advice (internship)

This is quite a rollercoaster of a story but I will try my best to explain this situation as best as possible. TL;DR will be provided at the end.

For some context, I am a university student in the UK and I am currently in a gap year. I have finished my second year and will be back at university this September for my final year.

Back in November 2023, I saw a posting for an internship (Big Oil company). It was a unique opportunity in that the department had just started operating in the UK and they were still recruiting for different roles across different tiers of seniority and building the department. Some key things to note about the role were that there was only one role available and it required an immediate start. I applied for the role and never really received communication for a while. Late in January, I received an email stating they would start to contact candidates and invite them to an assessment centre for the internship positions. In February I received an email inviting me to this assessment centre and that it was scheduled for the following week.

During the assessment centre, I was able to stand out and did well. I noticed one other candidate who also stood out and decided they would be my main competition. After the assessment centre, I decided to connect with them on LinkedIn and we exchanged numbers. We agreed to update each other on any communications we got from HR.

The day after the AC, they messaged me asking if I got the same email as them - I didn't. It was an email asking them to get on a call with HR to discuss the role. They got on a call the same day with HR and were notified that they got the role and discussed start dates and other key information. This candidate, however, was still studying and notified HR that they could not start immediately, but after their exams had finished.

The day after this, HR emailed me asking for my availability to start should I receive an offer, which I said I could start immediately. After I had replied to this email, I received a message from the candidate and they told me that their offer had been rescinded as they needed someone to start immediately. I then notified her that they did email me asking for my availability (a mistake on my part, I should've been a snake tbh).

The following week, on a Monday, HR emailed me the same email the other candidate initially got. "Would you get on a call to discuss the role?". I replied almost instantly saying I was available at any time for a call. However, I then got ghosted. I followed up the next day, and the day after, and still had no reply. I then received a message from the other candidate and they told me they called HR and negotiated that they would work part-time for now and transition into a full-time role after their exams had finished. (reason as to why I think F'd up by telling them).

I then got a rejection email a week later, after being ghosted by HR the whole time.

Now, fast forward from Feb to Monday this week. I got an email asking if I would still be interested in the role and if I could get on a call to discuss this. I responded by saying I was still interested. I got a reply back after about 2 hours saying they would talk with the hiring manager and schedule a call - which was then scheduled for 2 days.

During this call, I was praised by the hiring manager for my performance in the AC and told that I was initially the first pick. However, due to a standoff with HR, they had to go forward with another candidate. I was told that there was room in the budget for one more person and that the hiring manager wanted to go with me. The chat was about 15 minutes long and the hiring manager asked about my intentions to stay with the company, why I was interested, etc. At the end of the call, I was told that they wanted to go through with me and that I would receive an offer of employment soon.

TL;DR:
Got led on and then ghosted by HR two months ago for an internship, then they reached out to me recently and now I have been given an informal (verbal) offer.

My concern is that it has been two days and I have not received any further communication from anyone at the company. I have trust issues because of what has happened previously and wanted to know the best thing to do in my situation and if this (or anything similar) has been experienced by someone else.