What does the EU's carbon border adjustment mean for the UK?

The European Commission has proposed introducing a carbon border adjustment mechanism as part of the Green Deal, its flagship policy package. The mechanism – which has also been described as a carbon border tax – would place a cost on selected goods  entering the EU market to reflect the carbon emitted in their production. The proposal has raised concern amongst some of the EU’s trading partners, though little detail has so far been released by the European Commission on what shape the mechanism will take.