Governments will have no choice but to start using blockchain. Many have already started.
For the UK, blockchain will be really important for global trade in terms of supply chains, especially in the medicine, food and drink, recycling, chemicals, nuclear, tariffs and duties, and customs/borders areas.
This centralised government blockchain system will force industries and organisations to use that blockchain, but crucially, none of it would prevent parallel or private use of other blockchain platforms. So any individual or organisation would have their full blockchain, and they would only need to mirror the relevant transactions to the centralised government one.
I predict the country that implements such blockchain systems first will dominate a lot of global trade for a long time through its reduced costs, increased security, improved speed and just-in-time processes, ability to cut out cowboys before a smart contract payment is triggered, and would improve the livelihood of all concerned in that country.
And there is a global race going on right now to do just that, despite what Governments may publicly say about cryptocurrencies