Neil, one of the most worrying aspects is the replacement of CHIEF by CDS which Andrew Tyrie has already flagged up.
http://www.parliament.uk/documents/commons-committees/treasury/Correspondence/Tyrie-to-Nick-Lodge-relating-to-CDS-30-03-17.pdf
The original design specifications were for 60 million declarations a year and it will now have to cope with 300 million.
HMG has a 'history' of crap computer 'implementation' i.e. cancellations.
http://www.independent.co.uk/life-style/health-and-families/health-news/nhs-pulls-the-plug-on-its-11bn-it-system-2330906.html
Why the Hell they don't give these projects to Google/Amazon or even Deep Mind (though the latter would laugh at the project since it's simple data processing rather than AI) I just don't know.
We seem to be able to do difficult stuff like Tempora but are unable for example to pay my pension monthly (rather than four weekly) as it would take 'significant changes to the main State Pension computer' to quote from the Minister this week.
I despair. At least the e-passport system at Stansted allowed me to enter the country without fat Sandra from Border Force asking me stupid questions (though she was watching over the gates to make sure no-one held up a photo of someone else in front of their face which still fools it!)
The main Border Force computerisation was scrapped a couple of years ago at a cost of almost half a billion pounds. Good old Raytheon again.
http://www.newsweek.com/half-billion-pound-it-failure-has-left-britains-borders-vulnerable-268147