Hallwood did his PhD at Aberdeen in 1988 and his first degree at Hull. He is clearly not an expert on the UK economy judging by his recent, unusual, publications:

The FT published his letter as clickbait, I’m sure and I suspect he is better ignored but it is a remarkable idea that an academic, these days, seems to believe that England subsidises Scotland.

Does Scotland in Union have a US branch? Affiliated with the CIA?