Pros
I have been with the company previously and returned so that should help frame the review as a positive in most ways. The support you have from such a large organisation is massive and it seems like most people genuinely care and if there's any issues it's easy and encouraged to raise. Most of the work is engaging and interesting. Ironically compared to companies that don't work on as critical stuff it is a lot more relaxing maybe because of the longer time scales there's is very rarely a rush or forced overtime to complete. Overtime is always paid too. Pay increases are consistent every year with unions also pushing for a general pay rise to help with inflation. The companies future looks strong putting it in an excellent place financially.
Cons
Some of the technology and tools you have to use is incredibly dated and has long been surpassed by newer systems even 10-15 years ago. While some of this is linked to the security and support of legacy systems some of it is purely because "it's what we've always used" and any attempt to push for change usually falls on deaf ears. The amount of corporate speech and "briefs" can be draining and a waste of time. The push for a full return to office, while slow, is happening in some teams and it feels inevitable for a lot of people even when it benefits no one.