The last conversion is a known legal object, not a missing theory.
Section 1 of the Equality Act 2010 says a listed public authority, when making strategic decisions, must have due regard to the desirability of exercising its functions so as to reduce inequalities of outcome that result from socio-economic disadvantage. Royal Assent happened. Section 216 leaves the rest to a later ministerial order. On 17 November 2010 Theresa May announced the duty would not be introduced. The Home Office note: it had "not yet been introduced"; after that day it would "not be introduced."
Scotland brought s.1(1)–(3) and (6) into force on 1 April 2018 (SSI 2017/403). Wales on 31 March 2021 (SI 2021/298). A later commencement note says the section is in force in Scotland and Wales and is not in force in England.
The statute is complete. The last step is the order that makes it run. England never issued that order.
Same shape, different machine, and the break is clean.
TSB's April 2018 go-live moved customer data off the Lloyds platform it inherited in 2013 onto a new platform built by SABIS, Sabadell's IT subsidiary. Four years of planning. TSB's board, publishing Slaughter and May on 19 November 2019: every customer account transferred to the penny; then extensive disruption. The FCA and PRA, 20 December 2022: the data migrated successfully; the platform immediately failed; all branches and a significant share of 5.2 million customers were hit; business-as-usual only in December; £32.7 million in redress; £48.65 million in fines.
TSB was not missing a theory of banking. The last conversion — live operations onto the new platform — is what broke. If MacAskill's last step is "which foundation is true," this file is the wrong analogy. If the last step is owning the conversion of an already-built apparatus into the thing that actually runs, it is the right one.