(ii) Undue Influence
Where the claimant has transferred a benefit to the defendant as a result of undue influence, the influence may sometimes involve the exercise of pressure on the claimant to transfer the benefit. But this is not necessarily the case and consequently undue influence is more accurately analysed in terms of exploitation rather than compulsion.
(iii) Colore Officii
The ground of colore officii arises where a claimant is compelled to pay the defendant to secure the performance of a public duty which the defendant should perform for nothing or for less than the sum demanded. Whilst this ground of restitution is clearly founded on notions of compulsion, because it is a necessary condition that the public officer exerted illegitimate pressure to obtain the payment, it is more convenient to consider it in the context of restitutionary claims from public authorities. This is primarily because recent developments in this area of the law of restitution indicate that the ground of colore officii has been subsumed within a general ground of restitution involving the recovery of unauthorized payments made to public authorities.14