But is this actually a blockchain at all? Isn't it a signed database which could be central or distributed (with distributed not giving you any significant advantages but lots of downsides)?

I realise the word blockchain is trendy (which is probably why this 'chief scientist' has latched on to it), but it doesn't seem applicable to me to most of the problems faced in government, which are better solved by cryptography and a certain degree of centralisation of data. Why would we want a distributed NHS register of patients for example?

The security issues and complications with untrusted nodes and distributed consensus are legion, and the blockchain as used in bitcoin is a particularly inefficient way to address them (proof of work etc).