(i) State of the Authorities

Birks felt compelled to reconstruct his treatment of the grounds of restitution because he considered that recent decisions of the English courts meant that the absence of basis analysis was the only way of satisfactorily explaining the law. This was primarily because of the tranche of cases which he interpreted as recognizing that money paid pursuant to void interest rate swap transactions could be recovered simply by virtue of the fact that the transaction was void.⁷⁴ But absence of basis analysis has never been recognized by the courts and, despite Birks’s assertions to the contrary, the swaps cases do not compel its recognition.⁷⁵ Indeed, the orthodox approach requiring positive grounds of restitution to be established by the claimant has been specifically affirmed by the courts.⁷⁶ Most importantly, this was affirmed by the House of Lords in Deutsche Morgan Grenfell v IRC,⁷⁷ where the identification of a mistake was vital to the claim for restitution to enable the claimant to benefit from the extended limitation period under the Limitation Act 1980.⁷⁸