I don't know about that particular role, but I can say that many people work in public service knowing full well they could probably double their salary in the private sector, but do it anyway. Mainly because of the large amount of annual leave and a pension that is unbeatable in the private sector, but also the opportunity to do really interesting work in genuinely unique environment, rather than work for another food delivery startup.

While I understand that some people want to work in public service because they find the kind of work more meaningful; I think those reasons are a bit weak.

From what I can see, the annual leave for these roles is 30 days per year, this is nice but 25 days is pretty standard in most tech jobs in the UK, with some employers allowing you to sacrifice salary in exchange for more days (+ or - 5 days in exchange for equivalent days of salary)

I know the pension plan for civil service is particularly good, but I wonder how it compares in terms of actual pension pay with having worked for big tech and contribute part of a salary that is, as you said, probably double – plus company contributions or matching which can be quite high (5-10%). Also, the RSUs you get and yearly refreshers kinda become your pension plan for a lot of tech workers.

Life isn't all about money, but for most people money is the primary reason to choose one company over another.

Then I would suggest the public sector probably isn't for you, which is fine! But clearly, many people do enjoy working there and are quite happy with a lower salary.

The fact that we struggle massively to recruit people and that there are teams with a majority of contractors would suggest that perhaps there aren't enough people willing to look at the tradeoffs and maybe higher salaries would deliver better value for the tax payer ( we get paid a lot less than contractors)

Obviously anecdotal evidence regarding the above but still

I am a civil servant and while it's technically true that I could double my pay in the private sector, I would likely be on the top 1 percentile or higher.

I'd guess that salary is on the bottom 10 percentile for enterprise architects.

Edit

Pension is a good reason too, it is my main reason :)

Clicking through shows it to be on the low-end of that range, too, at £50,870. While I work in government UX and appreciate there's a level of serving one's country and fellow constituents, that is simply not enough salary to recruit a highly-qualified individual. Especially considering government services are under constant attack by nation-state threat actors, we should be hiring the best individuals to protect parliament.