AIB v Mark Redler isn't good.  The facts are reproduced in Jamie's post in detail, he clearly writes more quickly than me,

So, the case concerns the obligation of a trustee. 

A bank transfers funds to a solicitor that are to be held on trust for it. The trust is defeasible upon the solicitor paying out under the conditions specified by the bank. The solicitor pays the money away, but without having satisfied the conditions. The bank seeks to have the trust reconstituted (ie asks the solicitor to go to their own funds to put the money back). 

The solicitor argues that this is a claim analogous to a claim for damages, and that the bank is only entitled to be put in the position that they would have been in as if the breach of trust had not occurred. If they had paid out in accordance with the bank's instructions, much of the loss would still have been suffered anyway.

Infamously, in Target Holding v Redferns, Lord Browne-Wilkinson had characterised the claim as one for compensation for breach of trust, and had applied the same causal principles as one would to wrongdoing at common law. On the facts of that case that actually led to no different result as the condition which led to the trust being defeasible were in fact subsequently satisfied (in that case a charge of the requisite kind was executed). 

In AIB v Mark Redler the question arose whether Lord Browne-Wilkinson was right, in a case where it actually mattered because the conditions were never subsequently fulfilled.

The Supreme Court characterises the claim as one for equitable compensation for breach of trust (see Lord Toulson [64] and Lord Reed [133]). If this were correct, then only those losses which would not have been suffered but for the breach of trust should be recoverable, which is what the Supreme Court unanimously hold, endorsing Lord Browne-Wilkinson. If their characterisation of the nature of the claim were correct, there is no good reason for treating the claim in equity any differently from a claim for damages for wrongdoing at common law.

But that isn't the correct characterisation of the claim. The trustee is obliged to hold the fund transferred on trust. That obligation only comes to an end if the conditions are satisfied. The claim is to enforce the duties of the trustee, not claim compensation for their breach.

If a common law analogue is thought helpful, the correct one is the action for the agreed sum, not a claim for damages. If I open a bank account, and the bank pays away money credited to me otherwise than in accordance with my instructions, the money is still owed to me. It won't avail the bank to argue "if we had paid away the money in accordance with your instructions you would have lost it anyway". So what? The debt is still owing, and the fact that I would have lost the same sum anyway is neither here nor there.

I can't imagine other jurisdictions (eg Australia) will follow this. The relevant judicial authority and academic commentary was brought to the court's attention, and so I can't blame counsel as I like to do on occasions like this.

R