The case related to tax demands that were later held in judicial review proceedings to be ultra vires, and therefore void.

The Inland Revenue repaid the tax, but disputed their liability to pay interest on the money during the time which they had held it.

It paid the sums on a "without prejudice" basis, and then sought judicial review with a view to reclaiming the tax.

The problem was a claim based on mistake could not succeed, because Woolwich argued it was ultra vires from the start.

Nor was it duress colore officii because the Revenue was not impliedly threatening to withhold performance of a duty owed to Woolwich.