The Bank of England in 2017 set out Real-Time Gross Settlement (RTGS), service that deliver a payment system, only for UK based in cryptocurrency, is a infrastructure to access central bank money.
Proof of Concept (POC) was running in March 2018, the purpose was to understand how RTGS could be capable of supporting payment technologies, as those build on (DLT) Distributed Ledger Technology.
RTGS enable their system to connect and to achieve sttlement in central bank money. Essentially forms the foundation of what it does as a central bank. There is a condition: compatibility with blockchain if they achieve critical mass.