BAU
Atos, PA Consulting, Capgemini, EY, PA Consulting, IBM, and Sopra Steria all filled their boots at high margins largely because public pay restraints mean that the Civil Service and arms length bodies like NS&I are stopped from paying market rates to their staff and thus don't have many staff who understand how it all works. It's easy to blame poor management, but the main problem here is pay. A big shout out to the Tories who spent fourteen years reducing public sector pay, but Labour aren't much better.
Will this lesson be learned? Of course not, so the story will repeat an infinite number of times.