My doubtless faulty understanding was always that VAT was a European tax, that is, that it was imposed when we entered the common market as a sales tax. If that is the case, then why are we still paying VAT post Brexit?

Margaret, You are correct in that it was an EEC tax, but we had our own version, purchase tax, that it replaced.

VAT's a nice source of income for the government, so it won't be abolished!