When Leona Helmsley, the tyrannical hotel tycoon, drafted her will, the witness who signed it must have been a bit surprised. Helmsley bequeathed $12m (£6m) to Trouble, her beloved Maltese dog. Two of her four grandchildren were cut out of her will entirely.

The news sparked an uproar when it was made public in the press a few weeks ago. But the truth is that this difficult heiress from Manhattan is one of a line of wealthy, eccentric types who have opted to structure their wills creatively and set aside substantial sums to provide for their pets.