If only there was already a system that runs a legal case file digitally, with support for automating processes, with integration's to every system on the face of the planet, that is widely used by the legal industry already that includes a portal that allows various third parties to access selected data, and also allows you to upload and digitally sign things while meeting all of the stringent legal requirements of the legal sector.
Oh, that'll be Eclipse Legal's Proclaim, recently bought by Crapita to enter the legal software industry so it's even now owned by a government usual supplier.
Eclipse would sell you a perpetual license for £1000 per user, and probably with a further discount on that if you were buying 17,033 licenses assuming that you have a negotiator somewhat more competent than most civil servants or the PM who manages to reduce the price below the starting point. Yet, assuming they didn't then the total cost of the software would be £17,033,000.00
So 17 million plus some loose change, and you have the software required which comes with exceedingly user friendly and easy to use tools to create your own workflows that already have several thousand people available to do consulting to know how to use them effectively.
Scaling up the costs of moving a mid sized law firm to Proclaim, the entire job should be doable for ballpark £35 million, and would require about four months, assuming that the processes already exist and that the end locations have either a wireless network for mobile devices or desktops already in place.