Pitt v Holt  UKSC 26,  MHLO 46
As receiver under the MHA 1983 (old equivalent to deputy under the MCA 2005) for her husband, Mrs Pitt set up a settlement trust which overlooked the impact of inheritance tax; Futter's case did not involve the mental capacity. (1) The court considered the Hastings-Bass rule, and dismissed Mrs Pitt's appeal on this point (she had not breached her fiduciary duty so the settlement would not be set aside on this basis). (2) The court considered the test for setting aside a voluntary disposition on the ground of mistake, and allowed Mrs Pitt's appeal on this point.
Futter v HMRC; Pitt v HMRC!
Youtube, 'UK Supreme Court Judgments 9th May 2013 - Part 1' (9/5/13). Video of Lord Neuberger summarising the judgment.